![]() ![]() The Index Update and Sort operators consume 74% cost of the execution plan. The following execution plan is demonstrating an execution plan of the same query, but this query was completed within 130 seconds because of the added index, unlike the first one. We added a non-clustered index on Persons table before to update and the added index involves the PersonCityName and PersonPostCode columns as the index key. This query was completed within 68 seconds. The only difference is that this query updated the 3.000.000 rows of the Persons table. The following execution plan illustrates an execution plan of the previous query. Particularly, if we are working on the performance of the update query, we should take into account of this probability. Try Ubiq for free.Indexes are very helpful database objects to improve query performance in SQL Server. Ubiq makes it easy to visualize data, and monitor them in real-time dashboards. 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. Sometimes you may need to update a column in table based on value of another column in table. ![]()
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