Updated mysql section. (#7080)

* Update linux-quiz.md

- Previously there was a same questions in Q68 and Q88, and Q88 was removed. So added new question at Q88 of similar topic.

- Correct the answer of Q75, that is, option 4: not persistent.

* Update linux-quiz.md

Added reference link for Question no. 88

* Update php-quiz.md

Add 23 multi choice questions in php section.

* Updated mysql section.

Added 26 more quiz questions, that makes altogether 150 questions in the mysql (eng) section.

mysql/mysql-quiz.md

@@ -1199,3 +1199,187 @@ SELECT name FROM Students WHERE exam_score > 90;
 - [ ] SEARCH
 - [x] SELECT
 - [ ] EXTRACT
+
+
+
+#### Q125. Which MySQL function would you use to get the current date and time?
+
+- [ ]  GETDATE()
+- [ ]  CURRENTTIME()
+- [x]  NOW()
+- [ ]  DATETIME()
+
+#### Q126. In MySQL, which statement is used to add a new column to an existing table?
+
+- [ ]  MODIFY TABLE
+- [ ]  UPDATE TABLE
+- [x]  ALTER TABLE
+- [ ]  CHANGE TABLE
+
+#### Q127. What is the purpose of the LIMIT clause in a MySQL SELECT statement?
+
+- [ ]  To limit the number of tables that can be joined
+- [x]  To restrict the number of rows returned by the query
+- [ ]  To limit the number of columns that can be selected
+- [ ]  To restrict the query execution time
+
+#### Q128. Which MySQL command is used to show all databases on the server?
+
+- [ ]  LIST DATABASES;
+- [ ]  DISPLAY DATABASES;
+- [x]  SHOW DATABASES;
+- [ ]  SELECT DATABASES;
+
+#### Q129. What does the UNSIGNED keyword do when used in a column definition?
+
+- [ ]  It makes the column accept only positive numbers
+- [ ]  It makes the column accept only whole numbers
+- [x]  It doubles the maximum value that can be stored in the column
+- [ ]  It makes the column accept only text data
+
+#### Q130. Which MySQL function would you use to find the length of a string?
+
+- [ ]  SIZE()
+- [x]  LENGTH()
+- [ ]  LEN()
+- [ ]  STRLEN()
+
+#### Q131. What is the purpose of the AUTO_INCREMENT attribute in MySQL?
+
+- [ ]  To automatically update the column value when the row is modified
+- [ ]  To automatically decrease the column value by 1 for each new row
+- [x]  To automatically generate a unique identity for new rows
+- [ ]  To automatically set the column to the current timestamp
+
+#### Q132. Which MySQL statement is used to remove a table from a database?
+
+- [ ]  REMOVE TABLE
+- [ ]  DELETE TABLE
+- [x]  DROP TABLE
+- [ ]  ERASE TABLE
+
+#### Q133. What does the LIKE operator do in a WHERE clause?
+
+- [ ]  It compares two values for exact equality
+- [x]  It searches for a specified pattern in a column
+- [ ]  It checks if a value is NULL
+- [ ]  It performs mathematical comparisons
+
+#### Q134. Which MySQL function returns the number of rows affected by an INSERT, UPDATE, or DELETE statement?
+
+- [ ]  AFFECTED_ROWS()
+- [ ]  COUNT_CHANGES()
+- [ ]  ROW_COUNT()
+- [x]  FOUND_ROWS()
+
+#### Q135. What is the purpose of the HAVING clause in MySQL?
+
+- [ ]  To join multiple tables
+- [ ]  To sort the result set
+- [x]  To specify a search condition for a group or an aggregate
+- [ ]  To limit the number of rows returned
+
+#### Q136. Which MySQL statement is used to grant privileges to a user?
+
+- [ ]  ADD PRIVILEGES
+- [ ]  SET PRIVILEGES
+- [x]  GRANT
+- [ ]  ALLOW
+
+#### Q137. What does the IFNULL() function do in MySQL?
+
+- [ ]  It checks if a value is not NULL
+- [x]  It returns a specified value if the expression is NULL
+- [ ]  It sets a column value to NULL
+- [ ]  It removes NULL values from a result set
+
+#### Q138. Which MySQL command is used to show the current user and host?
+
+- [ ]  SHOW USER;
+- [ ]  CURRENT_USER();
+- [ ]  WHO AM I;
+- [x]  SELECT USER();
+
+#### Q139. What is the purpose of the EXPLAIN statement in MySQL?
+
+- [ ]  To provide documentation for a stored procedure
+- [ ]  To show the structure of a table
+- [x]  To show the execution plan of a SELECT statement
+- [ ]  To explain the meaning of an error message
+
+#### Q140. Which MySQL function would you use to round a number to the nearest integer?
+
+- [ ]  CEIL()
+- [ ]  FLOOR()
+- [x]  ROUND()
+- [ ]  INT()
+
+#### Q141. What does the UNIQUE constraint do in MySQL?
+
+- [ ]  It ensures that the column cannot contain NULL values
+- [x]  It ensures that all values in the column are different
+- [ ]  It automatically increments the value for each new row
+- [ ]  It sets a default value for the column
+
+#### Q142. Which MySQL statement is used to create an index on a table?
+
+- [ ]  ADD INDEX
+- [x]  CREATE INDEX
+- [ ]  MAKE INDEX
+- [ ]  INDEX TABLE
+
+#### Q143. What is the purpose of the COALESCE() function in MySQL?
+
+- [ ]  To combine multiple columns into one
+- [ ]  To check if all values in a list are equal
+- [x]  To return the first non-NULL value in a list
+- [ ]  To count the number of non-NULL values in a list
+
+#### Q144. Which MySQL command is used to start a transaction?
+
+- [ ]  BEGIN TRANSACTION
+- [ ]  START TRANSACTION
+- [ ]  INIT TRANSACTION
+- [x]  BEGIN
+
+#### Q145. What does the CONCAT() function do in MySQL?
+
+- [ ]  It adds numbers together
+- [x]  It joins two or more strings together
+- [ ]  It combines multiple rows into one
+- [ ]  It merges two tables
+
+#### Q146. Which MySQL statement is used to create a stored procedure?
+
+- [ ]  MAKE PROCEDURE
+- [ ]  ADD PROCEDURE
+- [x]  CREATE PROCEDURE
+- [ ]  DEFINE PROCEDURE
+
+#### Q147. What is the purpose of the REGEXP operator in MySQL?
+
+- [ ]  To perform mathematical operations
+- [ ]  To join multiple tables
+- [x]  To perform pattern matching using regular expressions
+- [ ]  To check if a value exists in a subquery
+
+#### Q148. Which MySQL function would you use to get the current user's username?
+
+- [ ]  CURRENT_USER()
+- [ ]  USERNAME()
+- [x]  USER()
+- [ ]  SYSTEM_USER()
+
+#### Q149. What does the DISTINCT keyword do in a SELECT statement?
+
+- [ ]  It sorts the result set in ascending order
+- [ ]  It limits the number of rows returned
+- [x]  It removes duplicate rows from the result set
+- [ ]  It selects only specific columns from the table
+
+#### Q150. Which MySQL statement is used to delete all rows from a table without deleting the table itself?
+
+- [ ]  DELETE TABLE
+- [ ]  REMOVE ALL FROM
+- [ ]  DROP TABLE
+- [x]  TRUNCATE TABLE