![]() ![]() SET employees.first_name = emp2.first_name Here’s an SQL query to update first_name column in employees table to first_name column in emp2 table. UPDATE first_table, second_table SET first_lumn1 = second_lumn2 WHERE first_table.id = second_table.table_id In such a case, you can use the following UPDATE statement syntax to update column from one table, based on value of another table. Mysql> insert into emp2(id, first_name, last_name)Īlso Read : Top MySQL Blogs for Database Administrators Both tables also have same id column values. Let us say you also have another table emp2(id, first_name, last_name) and you want to update first_name in employees table to first_name in emp2 table. You can also update column in one table from another column in a different table. With CASE statement, we can update our column value to various values, depending on the individual values of id column.Īlso Read : How to Fix Incorrect String Value in MySQL This is a much better approach than using WHERE clause because with WHERE clause we can only change a column value to one new value. We use a CASE statement to specify new value of first_name column for each value of id column. Here’s the SQL query to update first_name column based on value of id column using CASE statement. Update column based on another column using CASE statement In this case, all those rows whose id value matches one of the values returned by SELECT query, will be updated.Īlso read : How to Alter column from Null to Not Null You can also use another SELECT query in your WHERE clause as shown below. You can also use an IN operator in WHERE clause as shown below. You can also use logical operators like AND/OR in your WHERE clause as shown below. ![]() In the above statement, the UPDATE statement will first select rows that match the WHERE clause and update value of our column first_nameĪlso read : How to Escape Single quotes, special characters in MySQL ![]() Here’s the SQL query to update first_name column based on value of id columns using WHERE clause. Update column based on another column using WHERE clause There are two ways to update column based on value of another column – using WHERE clause and using CASE statement. Mysql> insert into employees(id, first_name, last_name)Īlso read : How to Update Multiple Columns in MySQL Let us say you have the following table employees(id, first_name, last_name) mysql> create table employees(id int, Here are the steps to update a column based on another column in SQL. How To Update a Column Based on Another Column in SQL Here is how to update a column based on another column in SQL Server, MySQL, PostgreSQL. HINT: For debugging reasons, you may comment out the "-select raise(ignore)" line.Sometimes you may need to update a column in table based on value of another column in table. Īdditionally, everything contained within the trigger will also consider updates performed recently, by the code itself (unlike a global update which first prepares the set to update and then executes, without considering the results of its proper update. You will notice that this trick is extremely fast, much faster than update with a where clause. Update real_table set val1 = new.val1, val2 = new.val2 where id = new.id Here is the code example: drop table if exists dummy Ĭreate temporary table dummy (id number, val1, val2) Ĭreate trigger dummy_ins before insert on dummy Instead of updating real_table, INSERT into DUMMY. Then formulate your query, however complex, containing joins, aggregates, withs. Here's a TRICK for complex updates: use a trigger on a dummy temporary table which never receives any records. ![]()
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