Merge pull request #348 from Deepak-Vohra/main

SQL-161 How to lock a single row in MySQL

Author: jzheaux

sql-queries-11/lock-single-row-mysql/access-mode-significance.sql

@@ -0,0 +1,16 @@
+SET TRANSACTION 
+READ ONLY;
+
+START TRANSACTION;
+SELECT * 
+FROM DEPARTMENT 
+WHERE id = 5 
+FOR UPDATE;
+
+SET TRANSACTION 
+READ ONLY;
+START TRANSACTION;
+SELECT * 
+FROM DEPARTMENT
+WHERE id = 5
+FOR SHARE;

sql-queries-11/lock-single-row-mysql/prereq-setup.sql

@@ -0,0 +1,4 @@
+DESC DEPARTMENT;
+
+SELECT * 
+FROM DEPARTMENT;

sql-queries-11/lock-single-row-mysql/select-for-share.sql

@@ -0,0 +1,31 @@
+// First Session
+START TRANSACTION;
+SELECT * 
+FROM DEPARTMENT 
+WHERE id = 5 
+FOR SHARE;
+
+// Second Session
+START TRANSACTION;
+SELECT * 
+FROM DEPARTMENT 
+WHERE id = 5 
+FOR SHARE;
+
+// Second Session
+SELECT * 
+FROM DEPARTMENT 
+WHERE id = 5 
+FOR UPDATE;
+
+// First Session
+COMMIT;
+
+// Second Session
+START TRANSACTION;
+UPDATE DEPARTMENT 
+SET code = 'MA' 
+WHERE id < 5 OR id > 5;
+
+SELECT * 
+FROM DEPARTMENT;

sql-queries-11/lock-single-row-mysql/select-for-update.sql

@@ -0,0 +1,30 @@
+// First Session
+START TRANSACTION;
+SELECT * 
+FROM DEPARTMENT 
+WHERE id = 5 
+FOR UPDATE;
+
+// Second Session
+SELECT * 
+FROM DEPARTMENT 
+WHERE id = 5 
+FOR SHARE;
+
+// First Session
+COMMIT;
+
+// Second Session
+START TRANSACTION;
+UPDATE DEPARTMENT 
+SET code = 'TEMP' 
+WHERE id < 5 OR id > 5;
+
+// First Session
+COMMIT
+// Second Session
+COMMIT;
+
+SELECT * 
+FROM DEPARTMENT;
+

sql-queries-11/lock-single-row-mysql/transaction-isolation-level-significance.sql

@@ -0,0 +1,7 @@
+SET 
+TRANSACTION ISOLATION LEVEL SERIALIZABLE;
+START TRANSACTION;
+SELECT * 
+FROM DEPARTMENT 
+WHERE id = 5;
+COMMIT;

sql-queries-11/lock-single-row-mysql/update-delete-insert.sql

@@ -0,0 +1,15 @@
+START TRANSACTION;
+UPDATE DEPARTMENT 
+SET code = 'MATH' 
+WHERE id = 5;
+COMMIT;
+
+INSERT 
+INTO DEPARTMENT(id, name, code) 
+VALUES(6, "Mathematics", "MA");
+
+START TRANSACTION; 
+DELETE 
+FROM DEPARTMENT 
+WHERE id = 6; 
+COMMIT;