FROM syntax shown in four of the other answers. If the source table is on the many side of a one-to-many join then it is undeterministic which of the possible matching joined records will be used in the Update an issue that MERGE avoids by raising an error if there is an attempt to update the same row more than once. This may be a niche reason to perform an update for example, mainly used in a procedure , or may be obvious to others, but it should also be stated that you can perform an update-select statement without using join in case the tables you're updating between have no common field.
I add this only so you can see a quick way to write it so that you can check what will be updated before doing the update. Since there are too many replies of this post, which are most heavily up-voted, I thought I would provide my suggestion here too. At first, I have created a table named with schoolold and inserted few records with respect to their column names and execute it. Then I created a new table named with schoolnew and similarly executed above actions on it. If you are using SQL Server you can update one table from another without specifying a join and simply link the two from the where clause.
This makes a much simpler SQL query:. In this Merge statement, we can do inset if not finding a matching record in the target, but exist in the source and please find syntax:. If the ID column name is the same in both tables then just put the table name before the table to be updated and use an alias for the selected table, i.
Of course this is not practical if I changed too many rows. Therefor the query in the original question would be best implemented in MySQL thusly:. I've not seen the a solution to the asked question in the other answers, hence my two cents.
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Dai k 24 24 gold badges silver badges bronze badges. Robin Day Robin Day If you are editing the the link between tables SET Table. CharlesWood yeah. I have the same question in MySQL. It would be great if someone knows how to implement it to MySQL and share with everyone.
How do I use an alias in set? Sebastian covers a technique for this in a recent blog post: sqlity. Show 3 more comments. This was around 10x quicker than the equivalent update Merge bugs: mssqltips. Your point? In this article, we will learn different methods that are used to update the data in a table with the data of other tables.
Mostly, we use constant values to change the data, such as the following structures. The full update statement is used to change the whole table data with the same value. This type of update statement is a bit complicated than the usual structures. In the following sections, we will learn how to write this type of update query with different methods, but at first, we have to prepare our sample data.
With the help of the following query, we will create Persons and AddressList tables and populate them with some synthetic data. These two tables have a relationship through the PersonId column, meaning that, in these two tables, the PersonId column value represents the same person. In this method, the table to be updated will be joined with the reference secondary table that contains new row values.
So that, we can access the matched data of the reference table based on the specified join type. Lastly, the columns to be updated can be matched with referenced columns and the update process changes these column values. After the execution of the update from a select query the output of the Persons table will be as shown below;.
After the SET keyword, we specified the column names to be updated, and also, we matched them with the referenced table columns. After the FROM clause, we retyped the table name, which will be updated. In addition to this, we can specify a WHERE clause and filter any columns of the referenced or updated table. We can also rewrite the query by using aliases for tables. Indexes are very helpful database objects to improve query performance in SQL Server.
Particularly, if we are working on the performance of the update query, we should take into account of this probability. The following execution plan illustrates an execution plan of the previous query. The only difference is that this query updated the 3. This query was completed within 68 seconds. 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.
The following execution plan is demonstrating an execution plan of the same query, but this query was completed within seconds because of the added index, unlike the first one. We have seen this obvious performance difference between the same query because of index usage on the updated columns. Some methods may be much faster than others, as they depend on your tables and the quantity of data.
Here are our SQL statements to create the tables. The sample code is similar for each database, but the data types are different. Our examples in this guide will show you how to update the person. This method is slightly different to the previous two. The join is performed in the Update clause, and not in the From clause. The Select query inside the Update statement looks up the two tables and constructs the right data set to use.
Then the Set clause will set the person account number to the account number value. This will happen depending on the tables and query that you have. Creating primary keys on the table may still result in this error.
This query will look up the right account number to use in the subquery, which joins to the outer person table and return it to the SET clause.
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