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20 wrz 2008 · Assuming that you want to insert/update single row, most optimal approach is to use SQL Server's REPEATABLE READ transaction isolation level: SET TRANSACTION ISOLATION LEVEL REPEATABLE READ; BEGIN TRANSACTION IF (EXISTS (SELECT * FROM myTable WHERE key=@key) UPDATE myTable SET ...
For each index entry, SQL Server will perform this modification as either an in-place update, or as a DELETE followed by an INSERT. SQL Server will use an in-place UPDATE whenever possible.
In SQL Server, and I believe/presume most other DBMS, your indexes are created based on specific columns you specify. Inserts and deletes will always affect an entire row, so there is no way they will not affect the index, but updates seem a bit more unique, they can specifically affect only certain columns.
23 sie 2018 · Indexing is a secret weapon to improve performance without modifying any code. Sometimes you must perform DML processes (insert, update, delete or combinations of these) on large SQL Server tables.
3 kwi 2008 · SQL Server covering indexes have gain much attention for performance tuning for SELECT statements, but little has been said on their effect on the UPDATE statement. This paper will...
10 lut 2023 · The INSERT statement is used to add new rows to a table. The INSERT is structured with the keyword INSERT, followed by the table name and sometimes optional but always good to include the schema that the table is part of. Next is the list of columns from the table.
5 maj 2021 · In this tip, we'll show you how you can use the T-SQL UPDATE statement to update data in a database table. We'll be using the AdventureWorks 2017 sample SQL database. If you want to follow along, you can download the sample database and restore it on your system.
