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Saleh Njohole

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Wednesday, December 3, 2025

PC TECHNICIAN QUESTIONS AND ANSWERS

By  No comments:


A. Computer Hardware (1–25)

  1. Which component is considered the “brain” of the computer?
    A. GPU
    B. CPU
    C. RAM
    D. SSD
    Answer: B

  2. Which device is used to store the computer’s BIOS settings?
    A. ROM
    B. CMOS battery
    C. HDD
    D. PSU
    Answer: B

  3. Which connector is used for modern internal hard drives?
    A. IDE
    B. SATA
    C. SCSI
    D. Parallel
    Answer: B

  4. RAM stands for:
    A. Random Access Memory
    B. Ready Active Memory
    C. Rapid Access Module
    D. Read Active Memory
    Answer: A

  5. Which slot is commonly used for graphics cards?
    A. PCI
    B. AGP
    C. PCIe x16
    D. ISA
    Answer: C

  6. A CPU cooler is used to:
    A. Increase performance
    B. Prevent overheating
    C. Clean dust
    D. Increase power
    Answer: B

  7. Which form factor is commonly used in desktop motherboards?
    A. ATX
    B. BTX
    C. NTX
    D. ITX
    Answer: A

  8. Which voltage is used by SATA power connectors?
    A. 12V, 5V, 3.3V
    B. 9V only
    C. 24V only
    D. 6V only
    Answer: A

  9. Which component stores temporary data while the computer is running?
    A. HDD
    B. RAM
    C. SSD
    D. NIC
    Answer: B

  10. SSD stands for:
    A. Solid State Drive
    B. Super Storage Disk
    C. Static Storage Device
    D. Secure System Drive
    Answer: A

  11. A Dual-Core processor has:
    A. 1 core
    B. 2 cores
    C. 4 cores
    D. 8 cores
    Answer: B

  12. Thermal paste is applied between:
    A. RAM and motherboard
    B. CPU and heatsink
    C. GPU and PSU
    D. HDD and case
    Answer: B

  13. Which device converts AC to DC power?
    A. GPU
    B. HDD
    C. PSU
    D. CPU
    Answer: C

  14. POST stands for:
    A. Power On Self Test
    B. Program Output System Test
    C. Primary Operating System Task
    D. Power Output Standard Test
    Answer: A

  15. Which port is used for older keyboards?
    A. USB
    B. PS/2
    C. HDMI
    D. VGA
    Answer: B

  16. Which connector is used for monitors?
    A. HDMI
    B. VGA
    C. DisplayPort
    D. All of the above
    Answer: D

  17. ECC RAM is used for:
    A. Gaming PCs
    B. Error correction
    C. Increasing heat
    D. Wireless connectivity
    Answer: B

  18. CPU speed is measured in:
    A. GHz
    B. MB
    C. Volts
    D. RPM
    Answer: A

  19. Which storage has no moving parts?
    A. HDD
    B. SSD
    C. Floppy disk
    D. CD-ROM
    Answer: B

  20. A GPU is responsible for:
    A. Power supply
    B. Network control
    C. Graphics rendering
    D. Memory management
    Answer: C

  21. Which cable is used for Ethernet?
    A. CAT6
    B. HDMI
    C. RCA
    D. USB
    Answer: A

  22. A motherboard chipset controls:
    A. Power input
    B. Data flow between CPU and components
    C. Sound quality
    D. Cooling system
    Answer: B

  23. Which type of memory is permanent?
    A. RAM
    B. Cache
    C. ROM
    D. Registers
    Answer: C

  24. HDDs are measured in:
    A. GHz
    B. RPM
    C. MBps
    D. kWh
    Answer: B

  25. Which pin count is used for DDR4 desktop RAM?
    A. 184
    B. 200
    C. 240
    D. 288
    Answer: D

B. Operating Systems (26–45)

  1. Windows system files usually have extension:
    A. .exe
    B. .dll
    C. .sys
    D. All of the above
    Answer: D

  2. Which key opens Task Manager quickly?
    A. Ctrl + S
    B. Ctrl + Alt + Del
    C. Alt + F4
    D. Win + R
    Answer: B

  3. Which OS is open-source?
    A. Windows
    B. macOS
    C. Linux
    D. ChromeOS
    Answer: C

  4. What does GUI stand for?
    A. General User Interaction
    B. Graphical User Interface
    C. Global User Internet
    D. Graphic Utility Item
    Answer: B

  5. Device drivers are used to:
    A. Connect hardware to the OS
    B. Update internet
    C. Remove viruses
    D. Boot faster
    Answer: A

  6. Windows command to check disk errors is:
    A. ipconfig
    B. chkdsk
    C. ping
    D. format
    Answer: B

  7. Which Windows feature restores system settings?
    A. Disk Cleanup
    B. Update Manager
    C. System Restore
    D. Task Scheduler
    Answer: C

  8. Which file system is best for Windows?
    A. NTFS
    B. FAT16
    C. EXT3
    D. HFS+
    Answer: A

  9. Safe Mode loads Windows with:
    A. All drivers
    B. Minimum drivers
    C. High performance settings
    D. Overclock settings
    Answer: B

  10. The Windows Run command shortcut:
    A. Win + R
    B. Win + X
    C. Win + S
    D. Win + Tab
    Answer: A

  11. Which tool shows system performance?
    A. Control Panel
    B. Device Manager
    C. Task Manager
    D. Notepad
    Answer: C

  12. Linux command to list files:
    A. copy
    B. ls
    C. cmd
    D. mkdir
    Answer: B

  13. The Windows registry stores:
    A. Hardware settings
    B. Software settings
    C. User preferences
    D. All of the above
    Answer: D

  14. Which OS update type includes security fixes only?
    A. Feature update
    B. Major update
    C. Patch
    D. Driver update
    Answer: C

  15. Which folder stores 64-bit applications in Windows?
    A. Program Files
    B. Program Files (x86)
    C. System32
    D. SysWOW64
    Answer: A

  16. The BIOS loads the OS by reading the:
    A. RAM
    B. Bootloader
    C. GPU
    D. USB port
    Answer: B

  17. Linux command to restart:
    A. restart now
    B. reboot
    C. shutdown /f
    D. refresh
    Answer: B

  18. Windows command to view IP address:
    A. ipconfig
    B. winip
    C. wmic
    D. ifconfig
    Answer: A

  19. Defragmentation is useful for:
    A. SSD
    B. HDD
    C. CMOS
    D. RAM
    Answer: B

  20. Which tool removes malware in Windows?
    A. Task Manager
    B. Windows Defender
    C. Disk Backup
    D. BIOS
    Answer: B

C. Networking (46–70)

  1. LAN stands for:
    A. Local Access Network
    B. Local Area Network
    C. Large Area Network
    D. Link Access Node
    Answer: B

  2. Common Wi-Fi standard:
    A. 802.11
    B. 909.11
    C. 505.20
    D. 702.10
    Answer: A

  3. What device connects multiple networks?
    A. Router
    B. Switch
    C. Hub
    D. Repeater
    Answer: A

  4. A switch works at which OSI layer?
    A. Layer 1
    B. Layer 2
    C. Layer 5
    D. Layer 7
    Answer: B

  5. IPv4 length:
    A. 16 bit
    B. 32 bit
    C. 64 bit
    D. 128 bit
    Answer: B

  6. Which command tests network connectivity?
    A. ipconfig
    B. ping
    C. netstat
    D. tracert
    Answer: B

  7. Which device broadcasts all traffic?
    A. Router
    B. Switch
    C. Hub
    D. Firewall
    Answer: C

  8. Default gateway refers to:
    A. Local router address
    B. MAC address
    C. DNS server
    D. IP lease
    Answer: A

  9. DNS translates:
    A. IP → URL
    B. URL → IP
    C. MAC → IP
    D. IP → Hostname only
    Answer: B

  10. Wi-Fi security type:
    A. WPA2
    B. HTTP
    C. FTP
    D. QRX
    Answer: A

  11. Subnet mask of a typical home network:
    A. 255.0.0.0
    B. 255.255.255.0
    C. 255.255.0.0
    D. 255.255.255.255
    Answer: B

  12. MAC address is:
    A. 32 bits
    B. 48 bits
    C. 64 bits
    D. 128 bits
    Answer: B

  13. Which command shows active connections?
    A. ping
    B. netstat
    C. gpupdate
    D. cls
    Answer: B

  14. CAT6 max speed:
    A. 100 Mbps
    B. 1 Gbps
    C. 10 Gbps
    D. 40 Gbps
    Answer: C

  15. Port for HTTP:
    A. 25
    B. 443
    C. 80
    D. 21
    Answer: C

  16. Port for FTP:
    A. 21
    B. 53
    C. 110
    D. 443
    Answer: A

  17. Port for DNS:
    A. 25
    B. 53
    C. 110
    D. 23
    Answer: B

  18. A repeater is used to:
    A. Filter malware
    B. Extend network signal
    C. Increase power supply
    D. Block websites
    Answer: B

  19. Firewall function:
    A. Video rendering
    B. Blocks unauthorized traffic
    C. Cleans RAM
    D. Formats HDD
    Answer: B

  20. Common wireless frequency:
    A. 1 GHz
    B. 2.4 GHz
    C. 10 GHz
    D. 0.5 GHz
    Answer: B

  21. Network topology with a central hub:
    A. Ring
    B. Mesh
    C. Star
    D. Bus
    Answer: C

  22. VPN is used for:
    A. Gaming
    B. Secure remote access
    C. Cooling
    D. Disk repair
    Answer: B

  23. Loopback IP:
    A. 192.168.0.1
    B. 10.0.0.1
    C. 8.8.8.8
    D. 127.0.0.1
    Answer: D

  24. Which tool checks path to a destination?
    A. ping
    B. tracert
    C. ls
    D. scanpath
    Answer: B

  25. RJ45 connector is used for:
    A. Power
    B. Keyboard
    C. Ethernet
    D. USB
    Answer: C

D. Troubleshooting & Safety (71–100)

  1. Which tool removes dust from a PC?
    A. Water
    B. Blower/compressed air
    C. Oil
    D. Paintbrush
    Answer: B

  2. ESD stands for:
    A. Electronic Storage Data
    B. Electrostatic Discharge
    C. Emergency System Device
    D. Electrical System Detector
    Answer: B

  3. Best surface to place a motherboard during repair:
    A. Metallic table
    B. Carpet
    C. Wood or non-conductive surface
    D. Wet cloth
    Answer: C

  4. PC beeps during startup indicates:
    A. Successful boot
    B. Hardware error
    C. Virus
    D. Low battery only
    Answer: B

  5. If PC does not power on, first check:
    A. GPU
    B. RAM
    C. Power cable & PSU
    D. Mouse
    Answer: C

  6. Overheating is commonly caused by:
    A. Too much RAM
    B. Bad cooling system
    C. Fast internet
    D. Keyboard error
    Answer: B

  7. Blue screen errors in Windows are called:
    A. BSA
    B. BSOD
    C. BSOS
    D. WSE
    Answer: B

  8. If no display appears, check:
    A. Monitor power
    B. GPU connection
    C. RAM
    D. All of the above
    Answer: D

  9. Which tool tests RAM?
    A. MemTest
    B. DiskPart
    C. WinZip
    D. BIOS updater
    Answer: A

  10. If computer auto-restarts, likely cause:
    A. Bad PSU
    B. Malware
    C. Overheating
    D. All of the above
    Answer: D

  11. CMOS battery type:
    A. AAA
    B. CR2032
    C. 9V
    D. AA
    Answer: B

  12. If hard drive not detected:
    A. Check SATA cable
    B. Check BIOS
    C. Check power connection
    D. All of the above
    Answer: D

  13. Which tool tests the PSU?
    A. Multimeter
    B. Screwdriver
    C. Flashlight
    D. HDMI cable
    Answer: A

  14. Which key enters BIOS?
    A. F1
    B. F2
    C. DEL
    D. Any of the above depending on PC
    Answer: D

  15. System freezing can be caused by:
    A. Bad RAM
    B. Overheating
    C. Malware
    D. All of the above
    Answer: D

  16. S.M.A.R.T. is related to:
    A. RAM
    B. HDD health
    C. GPU
    D. CPU temperature
    Answer: B

  17. If PC makes grinding noise:
    A. HDD failure
    B. GPU fan
    C. Case fan
    D. All possible
    Answer: D

  18. If keyboard not responding:
    A. Check USB port
    B. Test with another PC
    C. Replace keyboard
    D. All of the above
    Answer: D

  19. Which antivirus is built into Windows?
    A. Kaspersky
    B. Avast
    C. Windows Defender
    D. Bitdefender
    Answer: C

  20. To remove stubborn malware use:
    A. Windows Firewall
    B. System Restore
    C. Safe Mode + antivirus
    D. Notepad
    Answer: C

  21. SMART errors suggest:
    A. RAM failure
    B. HDD nearing failure
    C. Screen issue
    D. GPU crash
    Answer: B

  22. Unexpected shutdowns may be caused by:
    A. Overheating
    B. PSU failure
    C. Motherboard failure
    D. All of the above
    Answer: D

  23. To install OS from USB you must:
    A. Format USB
    B. Make it bootable
    C. Change boot priority
    D. All of the above
    Answer: D

  24. A burning smell inside PC indicates:
    A. Software error
    B. Hardware damage
    C. Browser problem
    D. Driver issue
    Answer: B

  25. If system time resets every boot:
    A. Virus
    B. CMOS battery dead
    C. PSU failure
    D. GPU problem
    Answer: B

  26. STOP error in Windows refers to:
    A. Slow PC
    B. BSOD
    C. Safe Mode
    D. Low memory
    Answer: B

  27. Tool to check memory usage:
    A. WinZip
    B. Task Manager
    C. Notepad
    D. CMD only
    Answer: B

  28. Which command repairs Windows boot files?
    A. bootrec /fixmbr
    B. ipconfig
    C. net stop
    D. cmdrepair
    Answer: A

  29. If PC powers but no display, try:
    A. Reseat RAM
    B. Reseat GPU
    C. Clear CMOS
    D. All of the above
    Answer: D

  30. Best practice after assembling a PC:
    A. Power it on immediately
    B. Check all connections first
    C. Install games first
    D. Shake the case
    Answer: B




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Tuesday, December 2, 2025

SQL TRIGGERS

By  No comments:

 C:\Users\ponjo>mysql -u root -p

Enter password:


MariaDB [(none)]> create database uni;

Query OK, 1 row affected (0.003 sec)


MariaDB [(none)]> create table students (

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> fname VARCHAR(100),

    -> age INT,

    -> gender ENUM('F','M'),

    -> ;

ERROR 1046 (3D000): No database selected

MariaDB [(none)]>

MariaDB [(none)]> use uni;

Database changed

MariaDB [uni]> CREATE TABLE courses (

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> course_name VARCHAR(100)

    -> );

Query OK, 0 rows affected (0.013 sec)


MariaDB [uni]> CREATE TABLE department (

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> dept_name VARCHAR(100)

    -> );

Query OK, 0 rows affected (0.018 sec)


MariaDB [uni]> CREATE TABLE students (

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> fname VARCHAR(100),

    -> age INT,

    -> gender ENUM('F','M'),

    -> course_id INT,

    -> dept_id INT,

    -> FOREIGN KEY (course_id) REFERENCES courses(id),

    -> FOREIGN KEY (dept_id) REFERENCES department(id)

    -> );

Query OK, 0 rows affected (0.038 sec)


MariaDB [uni]> CREATE TABLE grades (

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> student_id INT,

    -> course_id INT,

    -> grades VARCHAR(100),

    -> FOREIGN KEY (student_id) REFERENCES students(id),

    -> FOREIGN KEY (course_id) REFERENCES courses(id)

    -> );

Query OK, 0 rows affected (0.048 sec)


MariaDB [uni]> SHOW TABLES;

+---------------+

| Tables_in_uni |

+---------------+

| courses       |

| department    |

| grades        |

| students      |

+---------------+

4 rows in set (0.001 sec)


MariaDB [uni]> DESCRIBE courses;

+-------------+--------------+------+-----+---------+----------------+

| Field       | Type         | Null | Key | Default | Extra          |

+-------------+--------------+------+-----+---------+----------------+

| id          | int(11)      | NO   | PRI | NULL    | auto_increment |

| course_name | varchar(100) | YES  |     | NULL    |                |

+-------------+--------------+------+-----+---------+----------------+

2 rows in set (0.034 sec)


MariaDB [uni]> INSERT INTO courses(course_name) VALUES (

    -> 'BIT'),('ISM'),('SE'),('CS');

Query OK, 4 rows affected (0.063 sec)

Records: 4  Duplicates: 0  Warnings: 0


MariaDB [uni]> DESCRIBE departments;

ERROR 1146 (42S02): Table 'uni.departments' doesn't exist

MariaDB [uni]> DESCRIBE department;

+-----------+--------------+------+-----+---------+----------------+

| Field     | Type         | Null | Key | Default | Extra          |

+-----------+--------------+------+-----+---------+----------------+

| id        | int(11)      | NO   | PRI | NULL    | auto_increment |

| dept_name | varchar(100) | YES  |     | NULL    |                |

+-----------+--------------+------+-----+---------+----------------+

2 rows in set (0.031 sec)


MariaDB [uni]> INSERT INTO department(dept_name) VALUES (

    -> 'ICT'),('ACCOUNTS'),('HR'),('FINANCE');

Query OK, 4 rows affected (0.008 sec)

Records: 4  Duplicates: 0  Warnings: 0


MariaDB [uni]> DESCRIBE students;

+-----------+---------------+------+-----+---------+----------------+

| Field     | Type          | Null | Key | Default | Extra          |

+-----------+---------------+------+-----+---------+----------------+

| id        | int(11)       | NO   | PRI | NULL    | auto_increment |

| fname     | varchar(100)  | YES  |     | NULL    |                |

| age       | int(11)       | YES  |     | NULL    |                |

| gender    | enum('F','M') | YES  |     | NULL    |                |

| course_id | int(11)       | YES  | MUL | NULL    |                |

| dept_id   | int(11)       | YES  | MUL | NULL    |                |

+-----------+---------------+------+-----+---------+----------------+

6 rows in set (0.032 sec)


MariaDB [uni]> INSERT INTO students(fname,age,gender,course_id,dept_id)

    -> VALUES ('Mary',32,'F',2,1);

Query OK, 1 row affected (0.031 sec)


MariaDB [uni]> INSERT INTO students(fname,age,gender,course_id,dept_id)

    -> VALUES ('Jenny',28,'F',3,3),('Juma',40,'M',4,4);

Query OK, 2 rows affected (0.013 sec)

Records: 2  Duplicates: 0  Warnings: 0


MariaDB [uni]> DESCRIBE grades;

+------------+--------------+------+-----+---------+----------------+

| Field      | Type         | Null | Key | Default | Extra          |

+------------+--------------+------+-----+---------+----------------+

| id         | int(11)      | NO   | PRI | NULL    | auto_increment |

| student_id | int(11)      | YES  | MUL | NULL    |                |

| course_id  | int(11)      | YES  | MUL | NULL    |                |

| grades     | varchar(100) | YES  |     | NULL    |                |

+------------+--------------+------+-----+---------+----------------+

4 rows in set (0.025 sec)


MariaDB [uni]> INSERT INTO grades(student_id,course_id,grades) VALUES (

    -> 1,2,'A'),(2,3,'C'),(3,4,'B+');

Query OK, 3 rows affected (0.008 sec)

Records: 3  Duplicates: 0  Warnings: 0


MariaDB [uni]> SELECT * FROM courses;

+----+-------------+

| id | course_name |

+----+-------------+

|  1 | BIT         |

|  2 | ISM         |

|  3 | SE          |

|  4 | CS          |

+----+-------------+

4 rows in set (0.000 sec)


MariaDB [uni]> SELECT * FROM department;

+----+-----------+

| id | dept_name |

+----+-----------+

|  1 | ICT       |

|  2 | ACCOUNTS  |

|  3 | HR        |

|  4 | FINANCE   |

+----+-----------+

4 rows in set (0.000 sec)


MariaDB [uni]> SELECT * FROM students;

+----+-------+------+--------+-----------+---------+

| id | fname | age  | gender | course_id | dept_id |

+----+-------+------+--------+-----------+---------+

|  1 | Mary  |   32 | F      |         2 |       1 |

|  2 | Jenny |   28 | F      |         3 |       3 |

|  3 | Juma  |   40 | M      |         4 |       4 |

+----+-------+------+--------+-----------+---------+

3 rows in set (0.000 sec)


MariaDB [uni]> SELECT * FROM grades;

+----+------------+-----------+--------+

| id | student_id | course_id | grades |

+----+------------+-----------+--------+

|  1 |          1 |         2 | A      |

|  2 |          2 |         3 | C      |

|  3 |          3 |         4 | B+     |

+----+------------+-----------+--------+

3 rows in set (0.001 sec)


MariaDB [uni]> ALTER TABLE students ADD COLUMN created_at DATETIME;

Query OK, 0 rows affected (0.011 sec)

Records: 0  Duplicates: 0  Warnings: 0


MariaDB [uni]> SELECT * FROM students;

+----+-------+------+--------+-----------+---------+------------+

| id | fname | age  | gender | course_id | dept_id | created_at |

+----+-------+------+--------+-----------+---------+------------+

|  1 | Mary  |   32 | F      |         2 |       1 | NULL       |

|  2 | Jenny |   28 | F      |         3 |       3 | NULL       |

|  3 | Juma  |   40 | M      |         4 |       4 | NULL       |

+----+-------+------+--------+-----------+---------+------------+

3 rows in set (0.001 sec)


MariaDB [uni]> CREATE TRIGGER student_insert BEFORE INSERT ON students

    -> FOR EACH ROW SET NEW.created_at = NOW();

Query OK, 0 rows affected (0.011 sec)


MariaDB [uni]> INSERT INTO students(fname,age,gender,course_id,dept_id)

    -> VALUES ('Jackline',20,'F',3,3);

Query OK, 1 row affected (0.010 sec)


MariaDB [uni]> SELECT * FROM students;

+----+----------+------+--------+-----------+---------+---------------------+

| id | fname    | age  | gender | course_id | dept_id | created_at          |

+----+----------+------+--------+-----------+---------+---------------------+

|  1 | Mary     |   32 | F      |         2 |       1 | NULL                |

|  2 | Jenny    |   28 | F      |         3 |       3 | NULL                |

|  3 | Juma     |   40 | M      |         4 |       4 | NULL                |

|  4 | Jackline |   20 | F      |         3 |       3 | 2025-12-01 22:14:51 |

+----+----------+------+--------+-----------+---------+---------------------+

4 rows in set (0.001 sec)


MariaDB [uni]> SHOW TRIGGERS;

+----------------+--------+----------+----------------------------+--------+------------------------+-----------------------------------------------------+----------------+----------------------+----------------------+--------------------+

| Trigger        | Event  | Table    | Statement                  | Timing | Created                | sql_mode                                            | Definer        | character_set_client | collation_connection | Database Collation |

+----------------+--------+----------+----------------------------+--------+------------------------+-----------------------------------------------------+----------------+----------------------+----------------------+--------------------+

| student_insert | INSERT | students | SET NEW.created_at = NOW() | BEFORE | 2025-12-01 22:11:40.34 | NO_ZERO_IN_DATE,NO_ZERO_DATE,NO_ENGINE_SUBSTITUTION | root@localhost | cp850                | cp850_general_ci     | utf8mb4_general_ci |

+----------------+--------+----------+----------------------------+--------+------------------------+-----------------------------------------------------+----------------+----------------------+----------------------+--------------------+

1 row in set (0.024 sec)


MariaDB [uni]> CREATE TABLE student_backups (

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> fname VARCHAR(100),

    -> course_id INT,

    -> dept_id INT

    -> );

Query OK, 0 rows affected (0.019 sec)


MariaDB [uni]> CREATE TRIGGER student_backup AFTER INSERT ON students

    -> FOR EACH ROW INSERT INTO student_backups(fname,course_id,dept_id)

    -> VALUES (NEW.fname,NEW.course_id,NEW.dept.id);

Query OK, 0 rows affected (0.015 sec)


MariaDB [uni]> INSERT INTO students(fname,age,gender,course_id,dept_id)

    -> VALUES ('John',30,'M',3,3);

ERROR 1054 (42S22): Unknown column 'NEW.dept.id' in 'field list'

MariaDB [uni]> DROP TRIGGER student_backup;

Query OK, 0 rows affected (0.012 sec)


MariaDB [uni]> CREATE TRIGGER student_backup AFTER INSERT ON students

    -> FOR EACH ROW INSERT INTO student_backups(fname,course_id,dept_id)

    -> VALUES (NEW.fname,NEW.course_id,NEW.dept_id);

Query OK, 0 rows affected (0.017 sec)


MariaDB [uni]> INSERT INTO students(fname,age,gender,course_id,dept_id)

    -> VALUES ('John',30,'M',3,3);

Query OK, 1 row affected (0.010 sec)


MariaDB [uni]> SELECT * FROM student_backups;

+----+-------+-----------+---------+

| id | fname | course_id | dept_id |

+----+-------+-----------+---------+

|  1 | John  |         3 |       3 |

+----+-------+-----------+---------+

1 row in set (0.000 sec)


MariaDB [uni]> SELECT * students;

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'students' at line 1

MariaDB [uni]> SELECT * FROM students;

+----+----------+------+--------+-----------+---------+---------------------+

| id | fname    | age  | gender | course_id | dept_id | created_at          |

+----+----------+------+--------+-----------+---------+---------------------+

|  1 | Mary     |   32 | F      |         2 |       1 | NULL                |

|  2 | Jenny    |   28 | F      |         3 |       3 | NULL                |

|  3 | Juma     |   40 | M      |         4 |       4 | NULL                |

|  4 | Jackline |   20 | F      |         3 |       3 | 2025-12-01 22:14:51 |

|  6 | John     |   30 | M      |         3 |       3 | 2025-12-01 22:23:06 |

+----+----------+------+--------+-----------+---------+---------------------+

5 rows in set (0.000 sec)


MariaDB [uni]> ALTER TABLE students ADD COLUMN update_at DATETIME;

Query OK, 0 rows affected (0.015 sec)

Records: 0  Duplicates: 0  Warnings: 0


MariaDB [uni]> SELECT * FROM students;

+----+----------+------+--------+-----------+---------+---------------------+-----------+

| id | fname    | age  | gender | course_id | dept_id | created_at          | update_at |

+----+----------+------+--------+-----------+---------+---------------------+-----------+

|  1 | Mary     |   32 | F      |         2 |       1 | NULL                | NULL      |

|  2 | Jenny    |   28 | F      |         3 |       3 | NULL                | NULL      |

|  3 | Juma     |   40 | M      |         4 |       4 | NULL                | NULL      |

|  4 | Jackline |   20 | F      |         3 |       3 | 2025-12-01 22:14:51 | NULL      |

|  6 | John     |   30 | M      |         3 |       3 | 2025-12-01 22:23:06 | NULL      |

+----+----------+------+--------+-----------+---------+---------------------+-----------+

5 rows in set (0.001 sec)


MariaDB [uni]> CREATE TRIGGER update_student BEFORE UPDATE ON students

    -> FOR EACH ROW SET NEW.update_at = NOW();

Query OK, 0 rows affected (0.013 sec)


MariaDB [uni]> UPDATE students SET fname = 'Mariam' WHERE id=1;

Query OK, 1 row affected (0.011 sec)

Rows matched: 1  Changed: 1  Warnings: 0


MariaDB [uni]> SELECT * FROM students;

+----+----------+------+--------+-----------+---------+---------------------+---------------------+

| id | fname    | age  | gender | course_id | dept_id | created_at          | update_at           |

+----+----------+------+--------+-----------+---------+---------------------+---------------------+

|  1 | Mariam   |   32 | F      |         2 |       1 | NULL                | 2025-12-01 22:32:25 |

|  2 | Jenny    |   28 | F      |         3 |       3 | NULL                | NULL                |

|  3 | Juma     |   40 | M      |         4 |       4 | NULL                | NULL                |

|  4 | Jackline |   20 | F      |         3 |       3 | 2025-12-01 22:14:51 | NULL                |

|  6 | John     |   30 | M      |         3 |       3 | 2025-12-01 22:23:06 | NULL                |

+----+----------+------+--------+-----------+---------+---------------------+---------------------+

5 rows in set (0.001 sec)


MariaDB [uni]> SELECT * FROM grades;

+----+------------+-----------+--------+

| id | student_id | course_id | grades |

+----+------------+-----------+--------+

|  1 |          1 |         2 | A      |

|  2 |          2 |         3 | C      |

|  3 |          3 |         4 | B+     |

+----+------------+-----------+--------+

3 rows in set (0.001 sec)


MariaDB [uni]> CREATE TABLE grade_backup (

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> student_id INT,

    -> course_id INT,

    -> old_grade VARCHAR(100),

    -> new_grade VARCHAR(100),

    -> created_at DATETIME

    -> );

Query OK, 0 rows affected (0.015 sec)


MariaDB [uni]> CREATE TRIGGER student_update_backup AFTER UPDATE ON

    -> grades FOR EACH ROW INSERT INTO grade_backup(student_id,course_id,old_grade,new_grade,created_at)

    -> VALUES (OLD.student_id,OLD.course_id,OLD.grades,NEW.grades,NOW());

Query OK, 0 rows affected (0.017 sec)



MariaDB [uni]> UPDATE students SET fname = 'Mary' WHERE id=1;

Query OK, 1 row affected (0.002 sec)

Rows matched: 1  Changed: 1  Warnings: 0


MariaDB [uni]> SELECT * FROM grades;

+----+------------+-----------+--------+

| id | student_id | course_id | grades |

+----+------------+-----------+--------+

|  1 |          1 |         2 | A      |

|  2 |          2 |         3 | C      |

|  3 |          3 |         4 | B+     |

+----+------------+-----------+--------+

3 rows in set (0.004 sec)


MariaDB [uni]> UPDATE grades SET grades='C' WHERE id=1;

Query OK, 1 row affected (0.002 sec)

Rows matched: 1  Changed: 1  Warnings: 0


MariaDB [uni]> SELECT * FROM grades;

+----+------------+-----------+--------+

| id | student_id | course_id | grades |

+----+------------+-----------+--------+

|  1 |          1 |         2 | C      |

|  2 |          2 |         3 | C      |

|  3 |          3 |         4 | B+     |

+----+------------+-----------+--------+

3 rows in set (0.000 sec)


MariaDB [uni]> SELECT * FROM grade_backup;

+----+------------+-----------+-----------+-----------+---------------------+

| id | student_id | course_id | old_grade | new_grade | created_at          |

+----+------------+-----------+-----------+-----------+---------------------+

|  1 |          1 |         2 | A         | C         | 2025-12-01 22:48:15 |

+----+------------+-----------+-----------+-----------+---------------------+

1 row in set (0.000 sec)


MariaDB [uni]> CREATE TRIGGER delete_grades BEFORE DELETE ON grades

    -> FOR EACH ROW SIGNAL SQLSTATE'45000' SET MESSAGE_TEXT = 'You cant Delete Student Grade';

Query OK, 0 rows affected (0.008 sec)


MariaDB [uni]> DELETE FROM grade WHERE id=1;

ERROR 1146 (42S02): Table 'uni.grade' doesn't exist

MariaDB [uni]> DELETE FROM grades WHERE id=1;

ERROR 1644 (45000): You cant Delete Student Grade

MariaDB [uni]>

MariaDB [uni]>

MariaDB [uni]> CREATE TABLE deleted_grade(

    -> id INT PRIMARY KEY AUTO_INCREMENT,

    -> student_id INT,

    -> course_id INT,

    -> grade VARCHAR(100),

    -> deleted_at DATETIME

    -> );

Query OK, 0 rows affected (0.022 sec)


MariaDB [uni]> CREATE TRIGGER deleted_grade AFTER DELETE ON grades

    -> FOR EACH ROW INSERT INTO deleted_grade(student_id,course_id,grade,deleted_at)

    -> VALUES (OLD.student_id,OLD.course_id,OLD.grades,NOW());

Query OK, 0 rows affected (0.014 sec)


MariaDB [uni]> DROP TRIGGER delete_grades;

Query OK, 0 rows affected (0.016 sec)


MariaDB [uni]> DELETE FROM grade WHERE id=1;

ERROR 1146 (42S02): Table 'uni.grade' doesn't exist

MariaDB [uni]> DELETE FROM grades WHERE id=1;

Query OK, 1 row affected (0.004 sec)


MariaDB [uni]> select * FROM deleted_grade;

+----+------------+-----------+-------+---------------------+

| id | student_id | course_id | grade | deleted_at          |

+----+------------+-----------+-------+---------------------+

|  1 |          1 |         2 | C     | 2025-12-01 23:04:07 |

+----+------------+-----------+-------+---------------------+

1 row in set (0.001 sec)


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