If the string is in your external application (like PHP), sure, just construct the MySQL statement.
If the string is inside a MySQL table, you can’t. MySQL has no eval()
or such function. The following is impossible:
Suppose you have a table queries
with a field columnname
that refers to one of the column names in the table mytable
. There might be additional columns in queries
that allow you to select the columnname
you want.
INSERT INTO queries (columname) VALUES ("name")
SELECT (select columnname from queries) from mytable
You can however work with PREPARED STATEMENTS. Be aware this is very hacky.
SELECT columnname from queries into @colname;
SET @table="mytable";
SET @s = CONCAT('SELECT ',@colname,' FROM ', @table);
PREPARE stmt FROM @s;
EXECUTE stmt;