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Codage, syntaxe et commandes
Hello Kevin
This is the line from the help file I use in deciding to use REPLACE or UPDATE.
Unlike REPLACE, UPDATE - SQL uses record locking when updating multiple records in a table opened for shared access. This reduces record contention in multiuser situations, but may reduce performance. For maximum performance, open the table for exclusive use or use FLOCK( ) to lock the table.
When I need speed I use REPLACE.
If I think the records I am going to update may be locked I may use UPDATE.
However now that I do most things via VIEWS this situtation does not happen very oftens. For manipulation of my VIEWS prior to committing changes I almost always use replace to get the speed benefit.
>I am modifying an application that has many instances of multiple
>REPLACE commands to update tables, such as
>
>
>replace field1 with "value1"
>replace field2 with "value2"
>replace field3 with "value3"
>
>
>I want to speed this application up. So I considered:
>
>UPDATE MyTable;
> SET Field1 = "Value1";
> Field2 = "Value2"
> Field3 = "Value3"
>
>
>Since REPLACE starts at the first record, the 3 separate REPLACE commands
>therefore make 3 passes through the table, while the SQL Update goes through
>the table only once.
>
>However, the Hackers Guide says the SQL Update is slower than REPLACE. Isnt
>REPLACE 'old school' and SQL 'optimized'?
>
>What are the Pros and Cons of each method?
>
>Thanks
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