In SQL, is UPDATE always faster than DELETE+INSERT?
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Say I have a simple table that has the following fields:
- ID: int, autoincremental (identity), primary key
- Name: varchar(50), unique, has unique index
- Tag: int
I never use the ID field for lookup, because my application is always based on working with the Name field.
I need to change the Tag value from time to time. I'm using the following trivial SQL code:
UPDATE Table SET Tag = XX WHERE Name = YY;
I wondered if anyone knows whether the above is always faster than:
DELETE FROM Table WHERE Name = YY; INSERT INTO Table (Name, Tag) VALUES (YY, XX);
Again - I know that in the second example the ID is changed, but it does not matter for my application.
A bit too late with this answer, but since I faced a similar question, I made a test with JMeter and a MySQL server on same machine, where I have used:
- A transaction Controller (generating parent sample) that contained two JDBC Requests: a Delete and an Insert statement
- A sepparate JDBC Request containing the Update statement.
After running the test for 500 loops, I have obtained the following results:
DEL + INSERT - Average: 62ms
Update - Average: 30ms
In SQL, is UPDATE always faster than DELETE+INSERT?, A bit too late with this answer, but since I faced a similar question, I made a test with JMeter and a MySQL server on same machine, where I� Under the covers, the Storage Engine may implement UPDATE as delete + insert, or it can do an update in place. But I would assume than in either case, the UPDATE statement still faster than an DELETE + INSERT, since there is less overhead in the query processor.
The bigger the table (number of and size of columns) the more expensive it becomes to delete and insert rather than update. Because you have to pay the price of UNDO and REDO. DELETEs consume more UNDO space than UPDATEs, and your REDO contains twice as many statements as are necessary.
Besides, it is plain wrong from a business point of view. Consider how much harder it would be to understand a notional audit trail on that table.
There are some scenarios involving bulk updates of all the rows in a table where it is faster to create a new table using CTAS from the old table (applying the update in the the projection of the SELECT clause), dropping the old table and renaming the new table. The side-effects are creating indexes, managing constraints and renewing privileges, but it is worth considering.
What's better for large changes to a table: DELETE and INSERT , In this case, SQL Server will do a DELETE followed by an INSERT. But, I myself checked the Delete and Insert vs Update on a table that has� The UPDATE command is used to modify the records in the table. Upon executing this command the record values are modified based on values passed in the query. Along with WHERE clause you can update the specific records from the table. SQL UPDATE Syntax: Let’s see the basic syntax of DELETE command: UPDATE Table_Name SET ‘Column_Name
One command on the same row should always be faster than two on that same row. So the UPDATE only would be better.
EDIT set up the table:
create table YourTable (YourName varchar(50) primary key ,Tag int ) insert into YourTable values ('first value',1)
run this, which takes 1 second on my system (sql server 2005):
SET NOCOUNT ON declare @x int declare @y int select @x=0,@y=0 UPDATE YourTable set YourName='new name' while @x<10000 begin Set @x=@x+1 update YourTable set YourName='new name' where YourName='new name' SET @y=@y+@@ROWCOUNT end print @y
run this, which took 2 seconds on my system:
SET NOCOUNT ON declare @x int declare @y int select @x=0,@y=0 while @x<10000 begin Set @x=@x+1 DELETE YourTable WHERE YourName='new name' insert into YourTable values ('new name',1) SET @y=@y+@@ROWCOUNT end print @y
UPDATE is much faster than DELETE+INSERT sql server, UPDATE is much faster than DELETE+INSERT sql server , is that true always in SQL SERVER ? Please provide your thoughts. Thanks,. SQL HOME SQL Intro SQL Syntax SQL Select SQL Select Distinct SQL Where SQL And, Or, Not SQL Order By SQL Insert Into SQL Null Values SQL Update SQL Delete SQL Select Top SQL Min and Max SQL Count, Avg, Sum SQL Like SQL Wildcards SQL In SQL Between SQL Aliases SQL Joins SQL Inner Join SQL Left Join SQL Right Join SQL Full Join SQL Self Join SQL
Which is faster, Updates in Sql server result in ghosted rows - i.e. Sql crosses one row out and Should you always contain a "load_date" column when loading data into a database table? INSERT is also faster than DELETE and INSERT as a substitute for The above code updates 10000 rows at a time and the loop continues till @@rowcount has a value greater than zero. This ensures that the table is not locked. Best practices while updating large tables in SQL Server. 1. Always use a WHERE clause to limit the data that is to be updated 2.
Keep in mind the actual fragmentation that occurs when DELETE+INSERT is issued opposed to a correctly implemented UPDATE will make great difference by time.
Thats why, for instance, REPLACE INTO that MySQL implements is discouraged as opposed to using the INSERT INTO ... ON DUPLICATE KEY UPDATE ... syntax.
UPDATE Statement Performance in SQL Server, In this tip we look at doing updates for a large SQL Server table using a row It's a faster update than a row by row operation, but this is best used Always make sure you use a WHERE clause unless you want to update the entire table. used for the table, removing them could help optimize the update. In SQL, is UPDATE always faster than DELETE+INSERT? then answer is NO! Just google for "Expensive direct update"* "sql server" "deferred update"* "sql server" Such update(s) result in more costly (more processing) realization of update through insert+update than direct insert+update. These are the cases when
Fastest way to Delete Large Number of Records in SQL Server, By: Aaron Bertrand | Updated: 2019-12-03 | Comments (1) | Related: More Deleting large portions of a table isn't always the only answer. to most other tests, I bet that wouldn't be much faster than deleting one row or 10 rows at a time . - An "in-place update" (ie by changing a columns value to a new in the original row) or as a "not-in-place UPDATE" (DELETE followed by an INSERT). In place updates are the rule and are performed if possible. Here the rows stay exactly at the same location on the same page in the same extent. Only the bytes affected are chnaged.
What is the Difference Between Merge and Update?, Merge and Update are both used to modify data, but there are some differences. With MERGE, you're able to combine update, delete, and insert command into The UPDATE statement will most likely be more efficient than a MERGE if the�
More indexes, slower DELETE, The more indexes you add to a table, the slower DELETE becomes. That means deleting the row would be fast but finding would be very slow. Even delete and update statements have an execution plan. the database cannot use an index, although this is a special case that has its own SQL command: truncate table .
- as a practice, I'd never recommend updating the primary key column.
- @KM: I agree, this is a simplification of my real table, where all the lookup is done on a unique string field that is not the primary key. I do have a primary key int value that is completely irrelevant so I removed it from the example (it's automatically created and does not take part in the lookup at all)
- @KM: I updated the example to reflect the real table structure, just in case it makes a difference.
- UDPATE also has the benefit not to break any foreign key relations your table might have, as long as the key field being referenced doesn't change. If you DELETE + INSERT, some of your constraints might be violated and thus the DELETE might fail
- Related Read
- I would be curious to see the same stats with a large dataset and indexes.
- Hi Michael.That test was performed 5 years ago against the localhost (on a machine that doesn't exist anymore). To have some accuracy, the test should be repeated on identical tables and on indexed tables. Initial idea was just to grasp a flavor of the performance difference. If time allows it I may repeat it and update the post. I am glad that this post still sparks ppl's curiosity :)
- Are you basing this on any concrete data?
- @Rax Olgud, how do you answer that? You haven't even said what database you are using. You asked a conceptual question, yet want concrete data. If you want actual data then you will need to write a wile loop (on your system), and update the row 1000 times, write another loop that will delete/insert it 1000 times. and see what is faster.
- @Rax Olgud, there is some overhead in removing and creating an index value and checking any constraints. if you are just updating a data column it will avoid any of this overhead.
- @Mohy66, the measurement is the time it takes to run, the totaling of the rowcount is to verify the amount of work that was done during the test. Thanks for the down vote.
- The 'reshuffling' there would be the page split.