Modify MySQL Table ID DataType with FKs

modify_table_primary_key.sql

SET global group_concat_max_len = 4294967295;
SET @tableSchema = "SCHEMA_HERE";
SET @tableName = "TABLE_HERE";
SET @tablePrimaryDefinition = "int(10) unsigned not null auto_increment"; 
SET @referencedTablesColumnDefinition = "int(10) unsigned";
SELECT DISTINCT kcu.TABLE_NAME, 
                kcu.TABLE_SCHEMA, 
                kcu.COLUMN_NAME, 
                kcu.CONSTRAINT_NAME, 
                kcu.REFERENCED_TABLE_NAME, 
                kcu.REFERENCED_COLUMN_NAME, 
                kcu.REFERENCED_TABLE_SCHEMA, 
                cRef.UPDATE_RULE, 
                cRef.DELETE_RULE, 
                CONCAT(CONCAT('SET GLOBAL FOREIGN_KEY_CHECKS = 0'),
                       ';',
                       GROUP_CONCAT(DISTINCT 'ALTER TABLE ', kcu.TABLE_SCHEMA, '.', kcu.TABLE_NAME, ' DROP FOREIGN KEY ', kcu.CONSTRAINT_NAME SEPARATOR ';'), 
                       ';', 
                       GROUP_CONCAT(DISTINCT 'ALTER TABLE ', kcu.TABLE_SCHEMA, '.', kcu.TABLE_NAME, ' CHANGE ', kcu.COLUMN_NAME, ' ', kcu.COLUMN_NAME, ' ', @referencedTablesColumnDefinition SEPARATOR ';'), 
                       ';',
                       CONCAT('ALTER TABLE ', @tableSchema, '.', @tableName, ' CHANGE ', kcu.REFERENCED_COLUMN_NAME, ' ', kcu.REFERENCED_COLUMN_NAME, ' ', @tablePrimaryDefinition), 
                       ';',
                       GROUP_CONCAT(DISTINCT 'ALTER TABLE ', kcu.TABLE_SCHEMA, '.', kcu.TABLE_NAME, ' ADD CONSTRAINT ', kcu.CONSTRAINT_NAME, ' FOREIGN KEY(', kcu.COLUMN_NAME,') REFERENCES ', kcu.REFERENCED_TABLE_SCHEMA, '.', kcu.REFERENCED_TABLE_NAME, '(', kcu.REFERENCED_COLUMN_NAME, ') ON DELETE ', cRef.DELETE_RULE, ' ON UPDATE ', cRef.UPDATE_RULE SEPARATOR ';'),
                       ';',
                       CONCAT('SET GLOBAL FOREIGN_KEY_CHECKS = 1')
                ) AS query 
FROM   information_schema.KEY_COLUMN_USAGE AS kcu 
       JOIN information_schema.referential_constraints AS cRef ON ( cRef.CONSTRAINT_NAME = kcu.CONSTRAINT_NAME ) 
WHERE  kcu.referenced_table_name IS NOT NULL 
       AND kcu.REFERENCED_COLUMN_NAME IS NOT NULL
       AND kcu.REFERENCED_TABLE_SCHEMA = @tableSchema
       AND kcu.REFERENCED_TABLE_NAME = @tableName
GROUP  BY kcu.REFERENCED_TABLE_NAME

This SQL code will generate a query to update a table primary key definition, i.e.:
test_table.id BIG INT (20) NOT NULL AUTO INCREMENT to test_table.id INT(10) NOT NULL AUTO INCREMENT

How to use:

1. Change @tableSchema and @tableName to your requirements
2. Execute the query
3. Copy the generated query at the query column
4. Execute the generated query
5. See the magic happen!

What happens under the hood:

1. Generates the DROP FOREIGN KEY commands for all references
2. Change all column references to the target table with @referencedTablesColumnDefinition
3. Updates table's primary key with @tablePrimaryDefinition
4. Re-add all the foreign keys previously removed with ADD CONSTRAINT commands

The SET GLOBAL FOREIGN_KEY_CHECKS = 0/1 is necessary to avoid interruption of script because of data integrity errors.