Question

I wanna know how to get field value from dynamic query. I do it on stored-procedure in MySQL. I’ve the following code:

...
DECLARE l_query VARCHAR(500);
DECLARE l_table VARCHAR(50);

SET l_table = 'tb_user';
SET @l_query = concat('SELECT count(1) FROM ', l_table);
-- #Note that l_table will not always for tb_user,
-- it can be changed with other table name.

PREPARE l_sql FROM @l_query;
EXECUTE l_sql;
...

The question is, how to get value for count result (count(1)) ..?
I need this value, because it will be used on the next process at the same stored procedure.


Many thanks before.

Answer 1

Short: Use SELECT INTO to select the value into variable.

In your case:

...
DECLARE l_query VARCHAR(500);
DECLARE l_table VARCHAR(50);
DECLARE cnt INTEGER;

SET l_table = 'tb_user';
SET @l_query = concat('SELECT count(1) INTO @cnt FROM ', l_table);
-- #Note that l_table will not always for tb_user,
-- it can be changed with other table name.

PREPARE l_sql FROM @l_query;
EXECUTE l_sql;
-- Use cnt variable here
...