lookup_string

lookup_string(table_name, lookup_key, return_column)

This function looks up a value from a primary key table and evaluates it in the optimizer.

Arguments

table_name: The name of the table to lookup. Must be a primary-key table (VARCHAR). lookup_key: The key to lookup. Must be a string type (VARCHAR). return_column: The name of the column to return (VARCHAR).

Return Value

Returns a VARCHAR string containing the looked-up value. Returns NULL if not found.

Examples

Example 1: Return t2 table's event_day column value of t2 table with its primay key value equals to 1;

mysql> select lookup_string('t2', '1', 'event_day');
+---------------------------------------+
| lookup_string('t2', '1', 'event_day') |
+---------------------------------------+
| 2020-01-14                            |
+---------------------------------------+
1 row in set (0.02 sec)