From 2b42ef0287621de7bce0676d9bd030152e836903 Mon Sep 17 00:00:00 2001
From: "p.belezov" <p.belezov@mfc38.ru>
Date: Thu, 16 Jan 2025 14:09:11 +0800
Subject: [PATCH] identify lock

---
 MySQL/identify_lock.md                        | 29 +++++++++++++++++++
 .../all_foreign_keys_to_table_or_column.sql   | 21 --------------
 Readme.md                                     |  3 +-
 3 files changed, 31 insertions(+), 22 deletions(-)
 create mode 100644 MySQL/identify_lock.md
 delete mode 100644 MySQL/sql/all_foreign_keys_to_table_or_column.sql

diff --git a/MySQL/identify_lock.md b/MySQL/identify_lock.md
new file mode 100644
index 0000000..1b8a47d
--- /dev/null
+++ b/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;
+```
\ No newline at end of file
diff --git a/MySQL/sql/all_foreign_keys_to_table_or_column.sql b/MySQL/sql/all_foreign_keys_to_table_or_column.sql
deleted file mode 100644
index 58b937d..0000000
--- a/MySQL/sql/all_foreign_keys_to_table_or_column.sql
+++ /dev/null
@@ -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>';
\ No newline at end of file
diff --git a/Readme.md b/Readme.md
index 565981d..f4e444a 100644
--- a/Readme.md
+++ b/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)
\ No newline at end of file
+- - [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)
\ No newline at end of file