Merge pull request #377 from Deepak-Vohra/main

SQL-345 Updating Rows with a Subquery Referencing the Same Table in SQL

Author: xaeldung

sql-queries-12/updating-rows-subquery-referencing-same-table/mysql.sql

@@ -0,0 +1,18 @@
+-- Using a Self Join
+UPDATE Program AS P1
+JOIN (
+    SELECT id, DATE_ADD(start_date, INTERVAL 3 WEEK) AS new_end_date
+    FROM Program
+) AS P2
+ON P1.id = P2.id
+SET P1.end_date = P2.new_end_date;
+
+-- Using a Derived Table
+UPDATE Program
+SET end_date = (
+    SELECT new_end_date FROM (
+        SELECT DATE_ADD(start_date, INTERVAL 3 WEEK) AS new_end_date
+        FROM Program AS Temp
+        WHERE Temp.id = Program.id
+    ) AS Temp_table
+);

sql-queries-12/updating-rows-subquery-referencing-same-table/postgresql.sql

@@ -0,0 +1,13 @@
+-- Self-join
+UPDATE Program AS P1
+SET end_date = P2.start_date + INTERVAL '3 weeks'
+FROM Program AS P2
+WHERE P1.id = p2.id;
+
+-- Subquery within UPDATE ... SET
+UPDATE Program
+SET end_date = (
+    SELECT start_date + INTERVAL '3 weeks'
+    FROM Program AS Temp
+    WHERE Temp.id = Program.id
+);

sql-queries-12/updating-rows-subquery-referencing-same-table/sqlserver.sql

@@ -0,0 +1,14 @@
+-- Self join
+UPDATE P1
+SET P1.end_date = DATEADD(week, 3, P2.start_date)
+FROM Program AS P1
+JOIN Program AS P2
+ON P1.id = P2.id;
+
+--Subquery within UPDATE ... SET
+UPDATE Program
+SET end_date = (
+    SELECT DATEADD(week, 3, start_date)
+    FROM Program AS Temp
+    WHERE Temp.id = Program.id
+);