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MYSQL PREPARE Statements

PREPARE, EXECUTE and DEALLOCATE PREPARE Statements


PREPARE prepares a statement for execution

EXECUTE executes a prepared statement

DEALLOCATE PREPARE releases a prepared statement

SET @s = 'SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse';
PREPARE stmt2 FROM @s;
SET @a = 6;
SET @b = 8;
EXECUTE stmt2 USING @a, @b;

Result:


+------------+
| hypotenuse |
+------------+
| 10 |
+------------+

Finally,

DEALLOCATE PREPARE stmt2;

Notes:


.You must use @variables, not DECLAREd variables for FROM @s
.A primary use for Prepare, etc, is to 'construct' a query for situations where binding will not work, such as inserting the table name.

Alter table with add column


SET v_column_definition := CONCAT(
 v_column_name
 ,' ',v_column_type
 ,' ',v_column_options
);
SET @stmt := CONCAT('ALTER TABLE ADD COLUMN ', v_column_definition);
PREPARE stmt FROM @stmt;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;


Conclusion

In this page (written and validated by ) you learned about MYSQL PREPARE Statements . What's Next? If you are interested in completing MYSQL tutorial, your next topic will be learning about: MYSQL JSON.



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