Is there a function in mysql that tells what type the evaluated expression/column/literal is in a query? I don’t mean the information schema, but something like:
SELECT
TYPE('Washington') as literal_type,
TYPE(IF(col='a', col, 2)) as expression_type,
TYPE(col) as col_type
FROM table
And I would get something llike:
VARCHAR -- INT64 -- DATE
This is mainly for debugging purposes.
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Answer
No, there’s no function for what you’re describing.
The closest thing to what you’re talking about is using the MySQL client with the --column-type-info option to display result set metadata.
But that wouldn’t help you if you’re using SQL programmatically.
mysql> select 'Washington' as literal_type, if(d = 9, d, 2) as expression_type, t as col_type from mytable;
Output:
Field 1: `literal_type` Catalog: `def` Database: `` Table: `` Org_table: `` Type: VAR_STRING Collation: utf8mb4_0900_ai_ci (255) Length: 40 Max_length: 10 Decimals: 31 Flags: NOT_NULL Field 2: `expression_type` Catalog: `def` Database: `` Table: `` Org_table: `` Type: LONGLONG Collation: binary (63) Length: 20 Max_length: 1 Decimals: 0 Flags: BINARY NUM Field 3: `col_type` Catalog: `def` Database: `test` Table: `mytable` Org_table: `mytable` Type: DATE Collation: binary (63) Length: 10 Max_length: 10 Decimals: 0 Flags: BINARY +--------------+-----------------+------------+ | literal_type | expression_type | col_type | +--------------+-----------------+------------+ | Washington | 2 | 2020-11-21 | +--------------+-----------------+------------+ 1 row in set (0.00 sec)