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patternsqlMinor

Clear all tables with one DELETE

Submitted by: @import:stackexchange-dba··
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deletesqlstackoverflowmysqldba
tablesdeleteallwithoneclear

Problem

Is it possible to clear all tables with one request?
I have tried the following with no result.

DELETE a,b,c,d,e,f,g,h,i,j,k,l,m,n,o
FROM jos_bet_details as a, jos_bet_1x2 as b, jos_bet_1x2_best as c, jos_bet_1x2_prev as d,
     jos_bet_1x3 as e, jos_bet_1x3_best as f, jos_bet_1x3_prev g, jos_bet_hcp as h,
     jos_bet_hcp_best i, jos_bet_hcp_prev j, jos_bet_ou k,jos_bet_ou_best l,
     jos_bet_ou_prev m, jos_bet_debug n, jos_bet_deleted o

Solution

Here is your solution

SELECT CONCAT('DELETE ',delete_list,' FROM ',table_list)
INTO @mass_delete_table_command
FROM
(
    SELECT GROUP_CONCAT(table_name,'.*') delete_list,
    GROUP_CONCAT(table_schema,'.',table_name) table_list
    FROM
    (
        SELECT table_schema,table_name
        FROM information_schema.tables
        WHERE table_schema=database() AND
        table_name IN
        ('jos_bet_details','jos_bet_1x2','jos_bet_1x2_best','jos_bet_1x2_prev',
         'jos_bet_1x3','jos_bet_1x3_best','jos_bet_1x3_prev','jos_bet_hcp',
         'jos_bet_hcp_best','jos_bet_hcp_prev','jos_bet_ou','jos_bet_ou_best',
         'jos_bet_ou_prev','jos_bet_debug','jos_bet_deleted')
    ) ListOfTables
) DeleteParameters;
PREPARE s1 FROM @mass_delete_table_command;
EXECUTE s1;
DEALLOCATE PREPARE s1;


Here is the principle behind this: You want to use information_schema.tables to build the DELETE query dynamically for you.

First collect the names of the tables in a variable called 'mass_delete_table_command' as a delete list and a table list. Then, execute it as a prepared statement.

Here is sample code from creating 4 tables, adding records them, and zapping the records:

use test
DROP TABLE IF EXISTS t1;
DROP TABLE IF EXISTS t2;
DROP TABLE IF EXISTS t3;
DROP TABLE IF EXISTS t4;
CREATE TABLE t1 (n int NOT NULL);
CREATE TABLE t2 like t1;
CREATE TABLE t2 like t1;
CREATE TABLE t3 like t1;
CREATE TABLE t4 like t1;
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7);
INSERT INTO t2 SELECT * FROM t1;
INSERT INTO t3 SELECT * FROM t1;
INSERT INTO t4 SELECT * FROM t1;
SELECT A.*,B.*,C.*,D.* FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;
SELECT CONCAT('DELETE ',delete_list,' FROM ',table_list)
INTO @mass_delete_table_command
FROM
(
    SELECT GROUP_CONCAT(table_name,'.*') delete_list,
    GROUP_CONCAT(table_schema,'.',table_name) table_list
    FROM
    (
        SELECT table_schema,table_name
        FROM information_schema.tables
        WHERE table_schema=database() AND
        table_name IN ('t1','t2','t3','t4')
    ) ListOfTables
) DeleteParameters;
SELECT @mass_delete_table_command;
PREPARE s1 FROM @mass_delete_table_command;
EXECUTE s1;
DEALLOCATE PREPARE s1;
SELECT A.*,B.*,C.*,D.* FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;


I ran this in MySQL 5.5.12 on my PC. Here is the output:

```
mysql> use test
DROP TABLE IF EXISTS t1;
DROP TABLE IF EXISTS t2;
DROP TABLE IF EXISTS t3;
Database changed
mysql> DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (n int NOT NULL);
CREATE TABLE t2 like t1;
CREATE TABLE t2 like t1;
CREATE TABLE t3 like t1;
CREATE TABLE t4 like t1;
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7);
INSERT INTO t2 SELECT * FROM t1;
INSERT INTO t3 SELECT * FROM t1;
INSERT INTO t4 SELECT * FROM t1;
SELECT A.,B.,C.,D. FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;
SELECT CONCAT('DELETE ',delete_list,' FROM ',table_list)
INTO @mass_delete_table_command
FROM
(
SELECT GROUP_CONCAT(table_name,'.*') delete_list,
GROUP_CONCAT(table_schema,'.',table_name) table_list
FROM
(
SELECT table_schema,table_name
FROM information_schema.tables
WHERE table_schema=database() AND
table_name IN ('t1','t2','t3','t4')
) ListOfTables
) DeleteParameters;
SELECT @mass_delete_table_command;
PREPARE s1 FROM @mass_delete_table_command;
EXECUTE s1;
DEALLOCATE PREPARE s1;
SELECT A.,B.,C.,D. FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;
Query OK, 0 rows affected (0.04 sec)

mysql> DROP TABLE IF EXISTS t2;
Query OK, 0 rows affected (0.03 sec)

mysql> DROP TABLE IF EXISTS t3;
Query OK, 0 rows affected (0.03 sec)

mysql> DROP TABLE IF EXISTS t4;
Query OK, 0 rows affected (0.03 sec)

mysql> CREATE TABLE t1 (n int NOT NULL);
Query OK, 0 rows affected (0.07 sec)

mysql> CREATE TABLE t2 like t1;
Query OK, 0 rows affected (0.10 sec)

mysql> CREATE TABLE t2 like t1;
ERROR 1050 (42S01): Table 't2' already exists
mysql> CREATE TABLE t3 like t1;
Query OK, 0 rows affected (0.07 sec)

mysql> CREATE TABLE t4 like t1;
Query OK, 0 rows affected (0.25 sec)

mysql> INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7);
Query OK, 7 rows affected (0.08 sec)
Records: 7 Duplicates: 0 Warnings: 0

mysql> INSERT INTO t2 SELECT * FROM t1;
Query OK, 7 rows affected (0.05 sec)
Records: 7 Duplicates: 0 Warnings: 0

mysql> INSERT INTO t3 SELECT * FROM t1;
Query OK, 7 rows affected (0.07 sec)
Records: 7 Duplicates: 0 Warnings: 0

mysql> INSERT INTO t4 SELECT * FROM t1;
Query OK, 7 rows affected (0.06 sec)
Records: 7 Duplicates: 0 Warnings: 0

mysql> SELECT A.,B.,C.,D. FROM

Code Snippets

SELECT CONCAT('DELETE ',delete_list,' FROM ',table_list)
INTO @mass_delete_table_command
FROM
(
    SELECT GROUP_CONCAT(table_name,'.*') delete_list,
    GROUP_CONCAT(table_schema,'.',table_name) table_list
    FROM
    (
        SELECT table_schema,table_name
        FROM information_schema.tables
        WHERE table_schema=database() AND
        table_name IN
        ('jos_bet_details','jos_bet_1x2','jos_bet_1x2_best','jos_bet_1x2_prev',
         'jos_bet_1x3','jos_bet_1x3_best','jos_bet_1x3_prev','jos_bet_hcp',
         'jos_bet_hcp_best','jos_bet_hcp_prev','jos_bet_ou','jos_bet_ou_best',
         'jos_bet_ou_prev','jos_bet_debug','jos_bet_deleted')
    ) ListOfTables
) DeleteParameters;
PREPARE s1 FROM @mass_delete_table_command;
EXECUTE s1;
DEALLOCATE PREPARE s1;
use test
DROP TABLE IF EXISTS t1;
DROP TABLE IF EXISTS t2;
DROP TABLE IF EXISTS t3;
DROP TABLE IF EXISTS t4;
CREATE TABLE t1 (n int NOT NULL);
CREATE TABLE t2 like t1;
CREATE TABLE t2 like t1;
CREATE TABLE t3 like t1;
CREATE TABLE t4 like t1;
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7);
INSERT INTO t2 SELECT * FROM t1;
INSERT INTO t3 SELECT * FROM t1;
INSERT INTO t4 SELECT * FROM t1;
SELECT A.*,B.*,C.*,D.* FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;
SELECT CONCAT('DELETE ',delete_list,' FROM ',table_list)
INTO @mass_delete_table_command
FROM
(
    SELECT GROUP_CONCAT(table_name,'.*') delete_list,
    GROUP_CONCAT(table_schema,'.',table_name) table_list
    FROM
    (
        SELECT table_schema,table_name
        FROM information_schema.tables
        WHERE table_schema=database() AND
        table_name IN ('t1','t2','t3','t4')
    ) ListOfTables
) DeleteParameters;
SELECT @mass_delete_table_command;
PREPARE s1 FROM @mass_delete_table_command;
EXECUTE s1;
DEALLOCATE PREPARE s1;
SELECT A.*,B.*,C.*,D.* FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;
mysql> use test
DROP TABLE IF EXISTS t1;
DROP TABLE IF EXISTS t2;
DROP TABLE IF EXISTS t3;
Database changed
mysql> DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (n int NOT NULL);
CREATE TABLE t2 like t1;
CREATE TABLE t2 like t1;
CREATE TABLE t3 like t1;
CREATE TABLE t4 like t1;
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7);
INSERT INTO t2 SELECT * FROM t1;
INSERT INTO t3 SELECT * FROM t1;
INSERT INTO t4 SELECT * FROM t1;
SELECT A.*,B.*,C.*,D.* FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;
SELECT CONCAT('DELETE ',delete_list,' FROM ',table_list)
INTO @mass_delete_table_command
FROM
(
    SELECT GROUP_CONCAT(table_name,'.*') delete_list,
    GROUP_CONCAT(table_schema,'.',table_name) table_list
    FROM
    (
        SELECT table_schema,table_name
        FROM information_schema.tables
        WHERE table_schema=database() AND
        table_name IN ('t1','t2','t3','t4')
    ) ListOfTables
) DeleteParameters;
SELECT @mass_delete_table_command;
PREPARE s1 FROM @mass_delete_table_command;
EXECUTE s1;
DEALLOCATE PREPARE s1;
SELECT A.*,B.*,C.*,D.* FROM
(SELECT COUNT(1) t1count FROM t1) A,
(SELECT COUNT(1) t2count FROM t2) B,
(SELECT COUNT(1) t3count FROM t3) C,
(SELECT COUNT(1) t4count FROM t4) D;
Query OK, 0 rows affected (0.04 sec)

mysql> DROP TABLE IF EXISTS t2;
Query OK, 0 rows affected (0.03 sec)

mysql> DROP TABLE IF EXISTS t3;
Query OK, 0 rows affected (0.03 sec)

mysql> DROP TABLE IF EXISTS t4;
Query OK, 0 rows affected (0.03 sec)

mysql> CREATE TABLE t1 (n int NOT NULL);
Query OK, 0 rows affected (0.07 sec)

mysql> CREATE TABLE t2 like t1;
Query OK, 0 rows affected (0.10 sec)

mysql> CREATE TABLE t2 like t1;
ERROR 1050 (42S01): Table 't2' already exists
mysql> CREATE TABLE t3 like t1;
Query OK, 0 rows affected (0.07 sec)

mysql> CREATE TABLE t4 like t1;
Query OK, 0 rows affected (0.25 sec)

mysql> INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7);
Query OK, 7 rows affected (0.08 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> INSERT INTO t2 SELECT * FROM t1;
Query OK, 7 rows affected (0.05 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> INSERT INTO t3 SELECT * FROM t1;
Query OK, 7 rows affected (0.07 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> INSERT INTO t4 SELECT * FROM t1;
Query OK, 7 rows affected (0.06 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> SELECT A.*,B.*,C.*,D.* FROM
    -> (SELECT COUNT(1) t1count FROM t1) A,
    -> (SELECT COUNT(1) t2count FROM t2) B,
    -> (SELECT COUNT(1) t3count FROM t3) C,
    -> (SELECT COUNT(1) t4count FROM t4) D;
+---------+---------+---------+---------+
| t1count | t2count | t3count | t4count |
+---------+---------+---------+---------+
|       7 |       7 |       7 |       7 |
+---------+---------+---------+---------+
1 row in set (0.00 sec)

mysql> SELECT CONCAT('DELETE ',delete_list,' FROM ',table_list)
    -> INTO @mass_delete_table_command
    -> FROM
    -> (
    ->     SEL

Context

StackExchange Database Administrators Q#4984, answer score: 5

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