Force drop mysql bypassing foreign key constraint

user_229208 0
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I'm trying to delete all tables from a database except one, and I end up having the following error:

Cannot delete or update a parent row: a foreign key constraint fails

Of course I could trial and error to see what those key constraints are and eventually delete all tables but I'd like to know if there is a fast way to force drop all tables (as I'll be able to re-insert those I don't want deleted).

Google aimed me at some site that suggested the following method:

mysql> SET foreign_key_checks = 0;
mysql> drop table ...
mysql> SET foreign_key_checks = 1;

Short answer is it didn't really do the trick since I ended up receiving the same error while I was able to delete some more tables. I've seen on Stack Overflow ways to get all foreign keys linked to a certain table but that's way too time consuming unless I script it all (which is doable in the case there is no other option)

Database is 4.1 so I can't use DROP DATABASE

Ideas?

sql-drop foreign-keys mysql
7 Answers

Drop database exist in all versions of MySQL. But if you want to keep the table structure, here is an idea

mysqldump --no-data --add-drop-database --add-drop-table -hHOSTNAME -uUSERNAME -p > dump.sql

This is a program, not a mysql command

Then, log into mysql and

source dump.sql;

user_2323610

Simple solution to drop all the table at once from terminal.

This involved few steps inside your mysql shell (not a one step solution though), this worked me and saved my day.

Worked for Server version: 5.6.38 MySQL Community Server (GPL)

Steps I followed:

 1. generate drop query using concat and group_concat.
 2. use database
 3. turn off / disable foreign key constraint check (SET FOREIGN_KEY_CHECKS = 0;), 
 4. copy the query generated from step 1
 5. re enable foreign key constraint check (SET FOREIGN_KEY_CHECKS = 1;)
 6. run show table

MySQL shell

$ mysql -u root -p
Enter password: ****** (your mysql root password)
mysql> SYSTEM CLEAR;
mysql> SELECT CONCAT('DROP TABLE IF EXISTS `', GROUP_CONCAT(table_name SEPARATOR '`, `'), '`;') AS dropquery FROM information_schema.tables WHERE table_schema = 'emall_duplicate';
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| dropquery                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| DROP TABLE IF EXISTS `admin`, `app`, `app_meta_settings`, `commission`, `commission_history`, `coupon`, `email_templates`, `infopages`, `invoice`, `m_pc_xref`, `member`, `merchant`, `message_templates`, `mnotification`, `mshipping_address`, `notification`, `order`, `orderdetail`, `pattributes`, `pbrand`, `pcategory`, `permissions`, `pfeatures`, `pimage`, `preport`, `product`, `product_review`, `pspecification`, `ptechnical_specification`, `pwishlist`, `role_perms`, `roles`, `settings`, `test`, `testanother`, `user_perms`, `user_roles`, `users`, `wishlist`; |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> USE emall_duplicate;
Database changed
mysql> SET FOREIGN_KEY_CHECKS = 0;                                                                                                                                                   Query OK, 0 rows affected (0.00 sec)

// copy and paste generated query from step 1
mysql> DROP TABLE IF EXISTS `admin`, `app`, `app_meta_settings`, `commission`, `commission_history`, `coupon`, `email_templates`, `infopages`, `invoice`, `m_pc_xref`, `member`, `merchant`, `message_templates`, `mnotification`, `mshipping_address`, `notification`, `order`, `orderdetail`, `pattributes`, `pbrand`, `pcategory`, `permissions`, `pfeatures`, `pimage`, `preport`, `product`, `product_review`, `pspecification`, `ptechnical_specification`, `pwishlist`, `role_perms`, `roles`, `settings`, `test`, `testanother`, `user_perms`, `user_roles`, `users`, `wishlist`;
Query OK, 0 rows affected (0.18 sec)

mysql> SET FOREIGN_KEY_CHECKS = 1;
Query OK, 0 rows affected (0.00 sec)

mysql> SHOW tables;
Empty set (0.01 sec)

mysql>
user_14211100

Table1 {T_Id, T_Name, TT_Id(Nullable)(Foreign key on Table2 to the column TT_ID)}

Table2 {TT_ID,TT_Title}

1- make the foreign Key relation null able on the table1
2- update table1 set TT_ID = null where T_ID = ?
3- delete from table1

now you can have the table1 data delete and table2 data remain.

user_22565510
user_486840
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