Create fix-when-using-UPDATE-statement.sql

Author: dvohra09

sql-queries-11/how-to-interpret-and-fix-the-MySQL-Error-1093/fix-when-using-UPDATE-statement.sql

@@ -0,0 +1,37 @@
+-- This statement generates the Error 1093
+UPDATE Program 
+SET end_date = (SELECT start_date FROM Program);
+
+-- This statement fixes the Error 1093 in the preceding example using a derived table
+UPDATE Program
+SET end_date = (
+  SELECT subquery_program.start_date
+  FROM (
+    SELECT start_date
+    FROM Program 
+    WHERE description ='Major in Operating Systems'
+  ) AS subquery_program
+);
+
+-- This statement generates the Error 1093
+UPDATE Program
+SET name = (SELECT description FROM Program);
+
+-- This set of statements fixes the Error 1093 in the preceding example using a temporary table
+-- Create a temporary table 
+CREATE TEMPORARY TABLE IF NOT EXISTS temp_table AS
+SELECT id, description
+FROM Program;
+
+-- Update the main table using the temporary table
+UPDATE Program t
+JOIN temp_table temp ON t.id = temp.id
+SET t.name = temp.description;
+
+-- Drop the temporary table
+DROP TEMPORARY TABLE IF EXISTS temp_table;
+
+-- This statement fixes the Error 1093 using a self-join
+UPDATE Program p1
+JOIN Program p2 ON p1.id = p2.id
+SET p1.name = p2.description;