![]() ![]() concatenate the email into the emailList The following example illustrates how to use a cursor to iterate all rows in the employees table and concatenate the email into a string: DELIMITER $$ĭECLARE email_address VARCHAR( 100) DEFAULT "" ĭECLARE cur CURSOR FOR SELECT email FROM employees We’ll develop a stored procedure that creates an email list of all employees in the employees table in the sample database: The following diagram illustrates how MySQL cursor works. Notice that the handler declaration must appear after the variable and cursor declarations within the stored procedures. The finished is a variable to indicate that the cursor has reached the end of the result set. To declare a NOT FOUND handler, you use the following syntax: DECLARE CONTINUE HANDLER FOR NOT FOUND SET finished = 1 Code language: SQL (Structured Query Language) ( sql ) The handler is used to handle this condition. When the cursor reaches the end of the result set, it will not be able to retrieve the data, and a condition is raised. When working with MySQL cursor, you must also declare a NOT FOUND handler to manage the situation when the cursor cannot find any row.Įach time you call the FETCH statement, the cursor attempts to read the next row in the result set. It is a good practice to always close a cursor when it is no longer used. Then, retrieve the next row pointed by the cursor and advance the cursor to the subsequent row in the result set using the FETCH statement: FETCH cursor_name INTO variable1, variable2 Code language: SQL (Structured Query Language) ( sql )Īfter that, check if there is any row available before fetching it.įinally, deactivate the cursor and release the memory associated with it using the CLOSE statement: CLOSE cursor_name Code language: SQL (Structured Query Language) ( sql ) The OPEN statement initializes the result set for the cursor therefore, you must call the OPEN statement before fetching rows from the result set. Next, open the cursor using the OPEN statement: OPEN cursor_name Code language: SQL (Structured Query Language) ( sql ) ![]() Additionally, a cursor must always associate with a SELECT statement. If you declare a cursor before the variable declarations, MySQL will issue an error. The cursor declaration must come after any variable declaration. WHERE your_condition Code language: SQL (Structured Query Language) ( sql ) Here’s the basic syntax of a cursor: - declare a cursorįETCH cursor_name INTO variable1, variable2 ĬLOSE cursor_name Code language: PHP ( php )įirst, declare a cursor by using the DECLARE statement: DECLARE cursor_name CURSOR FOR SELECT column1, column2 Typically, you use cursors within stored procedures, triggers, and functions where you need to process individual rows returned by a query one at a time. In MySQL, a cursor is a database object used for iterating the result of a SELECT statement. Summary: in this tutorial, you will learn how to use MySQL cursor in stored procedures to iterate through a result set returned by a SELECT statement. ![]()
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