Question : I’m trying to diagnose an issue where 2 very similar queries are resulting in very different execution times, […]
Tag: execution-plan
Clustered Index Scan (Clustered) vs. Index Seek (NonClustered) + Key Lookup (Clustered)
Question : I have the following tables and content create table t(i int primary key, j int, k char(6000)) create […]
Hash keys probe and residual
Question : Say, we have a query like this: select a.*,b.* from a join b on a.col1=b.col1 and len(a.col1)=10 Assuming […]
Can’t reduce cost of query plan and get rid of Key Lookup because of cursor
Question : I have tried to create a non-clustered index on the fields that are in the output list which […]
Why is my query suddenly slower than it was yesterday?
Question : [Salutations] (check one) [ ] Well trained professional, [ ] Casual reader, [ ] Hapless wanderer, I have […]
Hash Match Spill
Question : I’ve got a hash match spill going on here. I’ve updated statistics with FULLSCAN on the tables involved […]
Why am I getting an implicit conversion of Int / Smallint to Varchar, and is it really impacting Cardinality Estimates?
Question : I’m trying to trouble shoot a slow performing query using Show Plan Analysis (SSMS) on the actual execution […]
Why does MySQL optimize query with “WHERE … OR” so badly?
Question : Hey there, this is my first question so please be patient if I miss to add something in […]
Unique filtered index and surprising estimation
Question : When I view the estimated execution plan for this query… SELECT * FROM tabela2 x LEFT JOIN dbo.tabela1 […]
Why is the secondary selective index not used when the where clause filters on `value()`?
Question : Setup: create table dbo.T ( ID int identity primary key, XMLDoc xml not null ); insert into dbo.T(XMLDoc) […]