How Can I Execute Multiple SQL Queries in a Single Statement Using PHP and MySQL?

Executing Multiple SQL Queries in a Single Statement with PHP

Introduction:
In certain scenarios, performing multiple SQL queries in a single statement provides efficiency and code readability benefits. This guide explores how to achieve this effectively in PHP using MySQL.

Query Execution with Multiple Statements:
To execute multiple SQL queries in one statement, specify a fifth parameter to the mysql_connect function, which represents a flag. Setting this flag to 65536 modifies the PHP behavior to allow multiple statements in a single call.

Example:

$conn = mysql_connect('localhost','username','password', true, 65536);
mysql_select_db('database_name');
mysql_query("
    INSERT INTO table1 (field1,field2) VALUES(1,2);

    INSERT INTO table2 (field3,field4,field5) VALUES(3,4,5);

    DELETE FROM table3 WHERE field6 = 6;

    UPDATE table4 SET field7 = 7 WHERE field8 = 8;

    -- etc
");

Considerations:

• When working with functions like mysql_fetch_* or mysql_num_rows, remember that only the first statement in the query is valid.
• If the first statement is an INSERT, you can only use mysql_affected_rows to determine the number of rows affected.
• If the first statement is a SELECT, you can use mysql_fetch_assoc or mysql_num_rows to retrieve data or count rows based on the select query.

Conclusion:
By leveraging multiple SQL queries in a single statement, you can enhance your code's efficiency and simplify its readability. This technique is particularly useful when performing common operations like data insertion, deletion, updates, and retrievals within a single request.

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