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.
Argumentsβ
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 Valueβ
Returns a VARCHAR string containing the looked-up value. Returns NULL
if not found.
Examplesβ
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)