Connect and share knowledge within a single location that is structured and easy to search. I have a temporary table containing the values and would like to update another table using those values. Perhaps something like this:. I'd modify Robin's excellent answer to the following:. Without a WHERE clause, you'll affect even rows that don't need to be affected, which could possibly cause index recalculation or fire triggers that really shouldn't have been fired.
This has the benefit that it is easy to run the SELECT statement on its own first to sanity check the results, but it does requires you to alias the columns as above if they are named the same in source and target tables. 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. Learn the importance of a great data stack. Discover why our customers rate Chartio 1.
Sign up for a day free trial. No credit card required. In a production environment, the later would be the preferred method.
For this test sample, we went with the simpler method of simply selecting all. Finally, when those match up, we update the target table with the corresponding values pulled from the source table by using the aliases assigned earlier in the script. A subquery is a query that is nested inside another query. It also allows for fine tuning exactly what you want the select statements to do and how they should behave. This one is a relatively easy script to follow. One thing you will notice that is different in this sample as opposed to the previous two, is this one is actually two different scripts that are independent of each other.
Each one updating the values of a single column. A look at the over-all execution plan for the JOIN option.
Notice that this returns in two parts. A quick look at the performance cost just on the "Clustered Index Scan" for each of these methods after updating the City and PostalCode columns. Now for the cleanup process if you choose to do so. You are certainly welcome to keep these new tables and the corresponding schema for future testing. Should you decide to remove them, the following block of code will remove the tables and schema from your AdventureWorks database.
This is due to the Primary-Foreign key constraint between the two tables. In this scenario, the two tables are Test. Person and Test. While any of these three options listed above are excellent ways of updating multiple rows at a time with distinct data, you the user, will find yourself leaning more toward one than another.
So, go with what is comfortable for you. However, you also may want to consider the performance cost of the option you choose from this SQL tutorial. On this simple example, the performance cost is minimal regardless of which option you select. On a larger database, it could be a resource hog. BusinessEntityID , p. FirstName , p. LastName , a.
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