In this method, the reference table can be thought of as a source table and the target table will be the table to be updated. The following query can be an example of this usage method. We have typed the Persons table after the MERGE statement because it is our target table, which we want to update, and we gave Per alias to it in order to use the rest of the query.
With the help of this syntax, the join condition is defined between the target and source table. In this last line of the query, we chose the manipulation method for the matched rows.
Finally, we added the semicolon ; sign because the MERGE statements must end with the semicolon signs. The major characteristic of the subquery is, they can only be executed with the external query. The noticeable difference in this method is, it might be a convenient way to update one column for the tables that have a small number of the rows.
Now we will execute the following query and then will analyze it. After the execution of the update from a select statement the output of the table will be as below;. As we can see, the PersonCityName column data of the Persons table have been updated with the City column data of the AddressList table for the matched records for the PersonId column.
Regarding this method, we should underline the following significant points. If the subquery finds more than one matched row, the update query will return an error, as shown below:. In this article, we learned to update the data in a table with the data where they are contained in other tables. PersonId INT. PersonName , PersonLastName. N 'Salvador' , N 'Williams' ,. Sign up for a day free trial. No credit card required. SOC 2 compliant. 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. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ask Question. Asked 11 years, 10 months ago. Active 3 months ago. Viewed 4. Improve this question. Nicholas Carey ID — Ali NajafZadeh. Add a comment. Active Oldest Votes. Improve this answer. Dai k 24 24 gold badges silver badges bronze badges. Robin Day Robin Day Below is the statement that is for the same: —. Let us see the table data. We can update the table rows based on the sub-query values as well.
Below is example for the same: —. Here if we discuss the above query, here first the sub-query gets executed and returns the value.
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