The [Address] table has values for both columns [PostCode] and [City]. This method uses SQL Joins for referencing the secondary table that contains values that need to be updated.
Therefore, the target table gets updated with the reference columns data for the specified conditions. The MERGE statement is useful for manipulating data in the target table based on the source table data for both matched and unmatched rows.
It is a straightforward method to update the existing table data from other tables. The merge join uses an inner join for matching data rows between the source and target data. It also has the maximum relative cost for sort operator. The subquery is the fastest method to update column data.
It uses the clustered index update and clustered index scan as highlighted. The subquery works efficiently, but it has its own limitations, as highlighted earlier.
The overall performance of your database depends on the table data, the number of updates, table relationships, indexes , and statistics.
SQL Server execution plans are a gateway for query optimizer and query executions. Just an arbitrary alias in this case. Adrian Macneil Adrian Macneil Shiva Patrick Frenette Patrick Frenette 6 6 silver badges 2 2 bronze badges.
Ryan Ryan 2, 6 6 gold badges 33 33 silver badges 45 45 bronze badges. I feel this should be the accepted answer, because it keeps things simple and to the point. Simon Hughes 3, 3 3 gold badges 23 23 silver badges 44 44 bronze badges.
Hentold Hentold 7 7 silver badges 11 11 bronze badges. What if we want to update Table2. BSMP 4, 8 8 gold badges 33 33 silver badges 43 43 bronze badges. Jason Clark Jason Clark 6 6 gold badges 17 17 silver badges 47 47 bronze badges. And if you wanted to join the table with itself which won't happen too often : update t1 -- just reference table alias here set t1. Aleksandr Fedorenko Aleksandr Fedorenko Richard Richard 1, 10 10 silver badges 13 13 bronze badges.
Consolidating all the different approaches here. Abdul Azeez Abdul Azeez 8 8 silver badges 18 18 bronze badges. Yaman Yaman 16 16 silver badges 31 31 bronze badges. Bartosz X Bartosz X 2, 23 23 silver badges 32 32 bronze badges. Or even use table variable like tbl, "on PermTable.
Have you tried? I am using a phone to reply this, no computer to try. Johannes Wentu Johannes Wentu 1 1 gold badge 12 12 silver badges 27 27 bronze badges. Cornezuelo del Centeno Cornezuelo del Centeno 7 7 silver badges 19 19 bronze badges. Mateen Mateen 1, 1 1 gold badge 19 19 silver badges 26 26 bronze badges. Govind Tupkar Govind Tupkar 2 2 silver badges 5 5 bronze badges. This answer turned up in the low quality review queue, presumably because you don't provide any explanation of the code.
If this code answers the question, consider adding adding some text explaining the code in your answer. This way, you are far more likely to get more upvotes — and help the questioner learn something new. Jesse 3, 6 6 gold badges 24 24 silver badges 37 37 bronze badges.
Santhana Santhana 4 4 silver badges 15 15 bronze badges. Did it work for you? I used exact same query but had errors when used inner join, alias coun't be resolved. However the co-related sub query worked perfectly.
I don't have the exact error logs but the alias A was being referenced before the assignment, which caused the error. I used the correlated sub query — pat capozzi. Rokonz Zaz Rokonz Zaz 1 1 silver badge 5 5 bronze badges. The Overflow Blog. Stack Gives Back I have SQL server Table in which there is column that I wanted to update according to a existing column value that is present in current row.
The CASE expression has two formats,. The simple CASE expression compares an expression to a set of simple expressions to determine the result. Both formats support an optional ELSE argument. Example Create SQL table that contains the below columns. In above table, I want to change state value i.
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