Please start any new threads on our new
site at https://forums.sqlteam.com. We've got lots of great SQL Server
experts to answer whatever question you can come up with.
| Author |
Topic |
|
bobbabuoy
Starting Member
33 Posts |
 Posted - 2004-05-17 : 07:21:22
|
| Can someone please help me understand when/how you should use parentheses when writing queries? My queries are working fine but I want them to work optimally well. Is there a tutorial out there?Thanks! |
|
|
nr
SQLTeam MVY
12543 Posts |
Posted - 2004-05-17 : 07:27:12
|
| parentheses normally won't affect the query plan but they may make the query more difficult to understand.I tend to use them just for or's and subqueries.==========================================Cursors are useful if you don't know sql.DTS can be used in a similar way.Beer is not cold and it isn't fizzy. |
 |
|
|
SamC
White Water Yakist
3467 Posts |
Posted - 2004-05-17 : 07:42:46
|
| Parentheses [known as brackets in the UK, but hey, they've got a sense of humor] are needed to set subqueries apart as in:SELECT Cola FROM Mytable WHERE Colb IN (SELECT ... )andSELECT SevenUp FROM ( SELECT ... FROM ... ) A |
|
|
|
ravilobo
Master Smack Fu Yak Hacker
1184 Posts |
Posted - 2004-05-17 : 08:28:54
|
| If you are doing something like below..5*10/10The position of bracket will deside the output..(5*10)/10 is differenr from 5*(10/10)Use them in mathematical expressions...------------------------I think, therefore I am |
|
|
|
nr
SQLTeam MVY
12543 Posts |
Posted - 2004-05-17 : 11:40:09
|
| >> (5*10)/10 is differenr from 5*(10/10)The result of those will be the same.(5*10)/11 5*(10/11)will be different due to integer arithmetic - but it's not a good idea to code like that as it's not very obvious what the intention is.==========================================Cursors are useful if you don't know sql.DTS can be used in a similar way.Beer is not cold and it isn't fizzy. |
|
|
|
jsmith8858
Dr. Cross Join
7423 Posts |
Posted - 2004-05-17 : 12:55:39
|
| and as Nigel alludes, NEVER mix AND's and OR's without using parenthesis, even if you know the default evaluation order and it always seems to work the way you like. Always fully parenthesize boolean expressions if an OR is involved.for JOINS, I never use them -- haven't seen the need yet. MS Access drives me crazy because JET SQL for whatever reason requires every join to be in parenthesises which makes it impossible to read.Speaking of MS Access, it also goes a little crazy and puts lots of parens around expressions and criteria, but most GUI code generaters do that including the query builder in EM.- Jeff |
|
|
|
|
|
|
Optimize Query