identify lock

MySQL/identify_lock.md

@@ -0,0 +1,29 @@
+# Identify what locking table
+
+## Method 1
+
+```
+SHOW open tables WHERE In_use > 0;
+```
+
+## Method 2
+
+```
+SELECT
+    OBJECT_SCHEMA, 
+    OBJECT_NAME, 
+    GROUP_CONCAT(DISTINCT EXTERNAL_LOCK)
+FROM 
+    performance_schema.table_handles 
+WHERE 
+    EXTERNAL_LOCK IS NOT NULL
+GROUP BY 
+    OBJECT_SCHEMA, 
+    OBJECT_NAME;
+```
+
+## Process list
+
+```
+SHOW PROCESSLIST;
+```

MySQL/sql/all_foreign_keys_to_table_or_column.sql

@@ -1,21 +0,0 @@
-# Find all tables whose foreign key refers to the table/column
-
-# BY TABLE
-SELECT 
-  TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME, REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAME
-FROM
-  INFORMATION_SCHEMA.KEY_COLUMN_USAGE
-WHERE
-  REFERENCED_TABLE_SCHEMA = (SELECT DATABASE()) AND
-  REFERENCED_TABLE_NAME = '<insert_table_name>';
-  
-  
-# BY TABLE COLUMN
-SELECT 
-  TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME, REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAME
-FROM
-  INFORMATION_SCHEMA.KEY_COLUMN_USAGE
-WHERE
-  REFERENCED_TABLE_SCHEMA = (SELECT DATABASE()) AND
-  REFERENCED_TABLE_NAME = '<insert_table_name>' AND
-  REFERENCED_COLUMN_NAME = '<insert_column_name>';

Readme.md

@@ -5,4 +5,5 @@ This is a repository with useful snippets of various kinds of code
 ## Structure
 
 - [MySQL](./src/branch/master/MySQL)
-- - [all_foreign_keys_to_table_or_column](./src/branch/master/MySQL/all_foreign_keys_to_table_or_column.md)
+- - [all_foreign_keys_to_table_or_column](./src/branch/master/MySQL/all_foreign_keys_to_table_or_column.md)
+- - [identify_lock](./src/branch/master/MySQL/identify_lock.md)