Updating data in sql

Prerequisites For all of these examples, please do the following: General Analysis In terms of transitioning your code to the new approach, I have yet to experience any performance issues with 1000's of records, but that seems to be the first concern.

If you test the approach and the overall performance is not an issue, then consider the approach.

When using FROM, one should ensure that the join produces at most one output row for each row to be modified.

The SQL UPDATE Query is used to modify the existing records in a table.

You can use the WHERE clause with the UPDATE query to update the selected rows, otherwise all the rows would be affected.

The basic syntax of the UPDATE query with a WHERE clause is as follows − ---- ---------- ----- ----------- ---------- | ID | NAME | AGE | ADDRESS | SALARY | ---- ---------- ----- ----------- ---------- | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | ---- ---------- ----- ----------- ---------- ---- ---------- ----- ----------- ---------- | ID | NAME | AGE | ADDRESS | SALARY | ---- ---------- ----- ----------- ---------- | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | Pune | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | ---- ---------- ----- ----------- ---------- If you want to modify all the ADDRESS and the SALARY column values in the CUSTOMERS table, you do not need to use the WHERE clause as the UPDATE query would be enough as shown in the following code block.

In some databases, such as Postgre SQL, when a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table.

This has been beneficial for us because in our environment because our business users provide data to us in the form of Excel spreadsheets.

Many of the situations end up translating to INSERT, UPDATE or DELETE code in one or more of our SQL Server databases.It also may be faster to perform a single UPDATE as is the case with the example above versus uploading (INSERT...SELECT) the data and then performing an UPDATE based on the new table.For information about entering new data in a database, see the article Add one or more records to a database.Read this section if you are new to Access or unfamiliar with the concepts behind relational databases.After the tables have been created and the data added, changing or updating data in the tables becomes one of the day-to-day processes in maintaining a database.

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