Is there a quick way to update many records in SQL?
I need to replace over 20,000 names with new names generated with CodeID.
For example: I have to update all lines containing "dog" (with CodeID 1) with "cat" and update all lines containing "horse" (with Code 2) with "bird", etc.
1st SQL statement: UPDATE animalTable SET cDescription
= "cat" WHERE CodeID
= 1
2nd SQL statement: UPDATE animalTable SET cDescription
= "bird" WHERE CodeID
= 2
These instructions work, but I need a faster way to do it because I have over 20,000 names.
Thanks in advance.
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This is the fastest way to do it.
Or do you want to update all records in one command?
you can do the update with a connection (Fixed Syntax ... Havent used this for a while)
UPDATE animalTable
INNER JOIN CodeTable ON animalTable.CodeID = CodeTable.ID
SET animalTable.cDescription = CodeTable.Description_1;
Another option is to split the updates into smaller batches, this will shorten the table lock time ... But the total update time will take longer (this is just a performance improvement with a high degree of accuracy). You can do this by updating only certain ranges of identifiers in each batch.
You can also have this data in a separate table. Since the data is not normalized. Take it out so it becomes more normalized.
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You might want to create a temporary table that contains the translation values and update based on that.
For example:
create table #TRANSLATIONS
(
from varchar(32),
to varchar(32)
)
Then insert the translation values:
insert into #TRANSLATIONS (from,to) values ('cat','dog')
Finally, update based on this:
update MYTABLE
set myvalue = t.to
where myvalue = t.from
from MYTABLE m,
#TRANSLATIONS t
(Untested, from the top of the head).
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Suppose you have a file like this:
1,cat 2,bird ...
I would write a script that reads this file and does an update on every line.
In PHP:
$f = fopen("file.csv","r")
while($row = fgetcsv($f, 1024)) {
$sql = "update animalTable set cDescription = '".$row[1]."' where CodeID = ".$row[0];
mysql_query($sql);
}
fclose($f);
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What you can do to speed it up is only to update those records that don't already have the value you want to assign.
UPDATE animalTable SET cDescription = "cat" WHERE CodeID = 1 AND cDescription != "cat"
This approach forces the command to update only those entries that are not already "cat".
Disclaimer: I hate cats.
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