How to list all columns in table with Sql trigger - mysql

Question

CREATE TRIGGER `table_triger_on_before_delete`
BEFORE DELETE ON `db`.`table`
FOR EACH ROW
INSERT INTO db_bkp.`table`
(col1, col2, col3)
VALUES
(OLD.col1, OLD.col2, OLD.col3)
I want to get this
(col1, col2, col3)
without type them one by one

Answer 1

If you're absolutely sure that the tables are with the same fields you can use simply that
CREATE TRIGGER `table_triger_on_before_delete`
BEFORE DELETE ON `db`.`table`
FOR EACH ROW
INSERT INTO db_bkp.`table`
SELECT * FROM `db`.`table` WHERE `you_primary_key`= OLD.`you_primary_key`
Becouse you row isn't deleted yet :)

Answer 2

It is possible to query the list of columns of a particular table from information_schema.columns table within MySQL.
However, in this case you need to create your insert statement using prepared statement because this allows you to create the sql command as a string and then you can execute it.
...
declare s_fields, s_sql varchar(1000); --length should depend on how many fields you have
select group_concat(column_name) into s_fields
from information_schema.columns
where table_name='yourtable'
group by table_name
limit 1;
set s_sql=concat('insert into tablename (',s_fields, ') values (', variable_holding_comma_separated_list_of_values,')');
prepare stmt from s_sql;
execute stmt;
deallocate prepare stmt;
...

Answer 3

I have modified the code from #Shadow. you must also include the schema name.
and also put it in backquotes to prevent spaces in the fieldnames.
...
DECLARE s_sql VARCHAR(1000); --length should depend ON how many fields you have
SELECT
CONCAT(
'insert into tablename ('
,GROUP_CONCAT(CONCAT('`',COLUMN_NAME,'`'))
,') values ('
,GROUP_CONCAT(CONCAT('`OLD`.`',COLUMN_NAME,'`')),
')'
)
INTO s_sql
FROM information_schema.columns
WHERE
TABLE_NAME='your_table'
AND
TABLE_SCHEMA='your_schema'
GROUP BY TABLE_NAME;
prepare stmt from s_sql;
execute stmt;
deallocate prepare stmt;
...
sample
MariaDB [your_schema]> SELECT
-> CONCAT(
-> 'insert into tablename ('
-> ,GROUP_CONCAT(CONCAT('`',COLUMN_NAME,'`'))
-> ,') values ('
-> ,GROUP_CONCAT(CONCAT('`OLD`.`',COLUMN_NAME,'`')),
-> ')'
-> )
-> INTO #s_sql
-> FROM information_schema.columns
-> WHERE
-> TABLE_NAME='your_table'
-> AND
-> TABLE_SCHEMA='your_schema'
-> GROUP BY TABLE_NAME;
Query OK, 1 row affected (0.00 sec)
MariaDB [your_schema]> select #s_sql;
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| #s_sql |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| insert into tablename (`sr_no`,`scholar_no`,`paid_amount`,`due_amount`,`fee_date`,`section_id_fk`) values (`OLD`.`sr_no`,`OLD`.`scholar_no`,`OLD`.`paid_amount`,`OLD`.`due_amount`,`OLD`.`fee_date`,`OLD`.`section_id_fk`) |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
MariaDB [your_schema]>