Do something if a table exists - mysql

Question

I am trying to find out if there a table called OOK and if so, do something to it. This is what I have so far, which does not work with a helpful ERROR 1064 […] syntax error message:
IF show tables like 'OOK' THEN
DELETE FROM OOK WHERE Id = 'Development';
INSERT INTO OOK VALUES ( 'Development', 'Localhost' );
END IF
This is to support some legacy code and might not be the best solution to the problem. However, it will fix it for what I need.
Since I am getting lots of syntax errors on the answers, here is the exact version I have: Server version: 5.5.60-MariaDB MariaDB Server.

Answer 1

You can access Information Schema, to check if the table exists or not. Also, you will need to use Dynamic SQL (to handle the case when table name does not exist)
Try something like below:
IF EXISTS (SELECT 1
FROM information_schema.tables
WHERE table_schema = 'your_database_name'
AND table_name = 'OOK') THEN
SET #s1 = 'DELETE FROM your_database_name.OOK WHERE Id = ?';
SET #a = 'Development';
PREPARE stmt1 FROM #s1;
EXECUTE stmt1 USING #a;
DEALLOCATE PREPARE stmt1;
SET #s2 = 'INSERT INTO your_database_name.OOK VALUES (?, ?)';
SET #b = 'Development';
SET #c = 'Localhost';
PREPARE stmt2 FROM #s2;
EXECUTE stmt1 USING #b, #c;
DEALLOCATE PREPARE stmt2;
END IF

Answer 2

I use the procedure and the function below in a table duplication process in a db:
Usage
CALL do_something('mydb', 'OOK', 'Development', 'Development', 'Localhost');
Implementation
DELIMITER $$;
CREATE PROCEDURE do_something(
IN dbName VARCHAR(255),
IN tableName VARCHAR(255),
IN id VARCHAR(255),
IN value1 VARCHAR(255),
IN value2 VARCHAR(255)
)
BEGIN
IF ( fn_table_exists(dbName, tableName) )
THEN
CALL statement(CONCAT(
'DELETE FROM ', tableName, ' WHERE Id = "', id, '"'));
CALL statement(CONCAT(
'INSERT INTO ', tableName, ' VALUES ( "', value1, '", "', value2, '" )'));
ELSE
SELECT CONCAT(
'ERROR: Table "', tableName, '" does not exist in the schema "', dbName, '".'
) AS ErrorMessage;
END IF;
END$$
DELIMITER ;
DELIMITER $$;
CREATE PROCEDURE statement(IN dynamic_statement TEXT)
BEGIN
SET #dynamic_statement := dynamic_statement;
PREPARE prepared_statement FROM #dynamic_statement;
EXECUTE prepared_statement;
DEALLOCATE PREPARE prepared_statement;
END$$
DELIMITER ;
DELIMITER $$;
CREATE FUNCTION fn_table_exists(dbName VARCHAR(255), tableName VARCHAR(255))
RETURNS TINYINT(1)
BEGIN
DECLARE totalTablesCount INT DEFAULT (
SELECT COUNT(*)
FROM information_schema.TABLES
WHERE (TABLE_SCHEMA COLLATE utf8_general_ci = dbName COLLATE utf8_general_ci)
AND (TABLE_NAME COLLATE utf8_general_ci = tableName COLLATE utf8_general_ci)
);
RETURN IF(
totalTablesCount > 0,
TRUE,
FALSE
);
END$$
DELIMITER ;