Lab Sql

If I run the following SQL query SELECT * FROM A LEFT JOIN B ON A.foo=B.foo WHERE A.date = 'Ye… Read more Sql Order Of Operations

We see an issue occasionally. Stored procedure running a SQL runs very slow. Same SQL when run fro… Read more Db2 Luw 10.5 - How To Force Db2 Stored Procedures To Use Latest Stats For Most Optimized Plan

Say I have 2 functions using third one. Say function check_permission(user_id) is used by get_compa… Read more Postgresql Function Execution Plan Cache Principle

I'm experiencing a strange behaviour in a specific query in the SQL Server 2008 R2. I've go… Read more A Query That Does A Lot Of Reads, But Plan Is Ok

I have a SQL database server and 2 databases under it with the same structure and data. I run the s… Read more The Same Sql Query Takes Longer To Run In One Db Than Another Db Under The Same Server

Is there any difference? I know SQL queries are having their execution plans cached just as good as… Read more Postgresql Performance Of Ad-hoc Sql Vs Functions

In PostgreSQL, I have an index on a date field on my tickets table. When I compare the field agains… Read more Efficient Postgresql Query On Timestamp Using Index Or Bitmap Index Scan?

I have a table and data like this: create table AmountObjects ( objectId integer, unixTimestamp… Read more How Do Not Scan All Records To Query Top Rows By Complex Condition

I have noticed that Apache Flink does not optimise the order in which the tables are joined. At th… Read more Apache Flink - Enable Join Ordering

I'm trying to debug a fairly complex stored procedure that joins across many tabls (10-11). I&#… Read more How Does Sql Server Work Out The Estimated Number Of Rows?

I know I can change the way MySQL executes a query by using the FORCE INDEX (abc) keyword. But is t… Read more Is There A Way To Force Mysql Execution Order?

I cannot get a select statement (very last line in the script below) to query rewrite to use a mate… Read more Query Rewrite Fails If Mv Uses Asni Join

I'm looking for an application to display what a linq expression would do, in particular regard… Read more Is There An Application For Displaying Some Kind Of Query Plan For A Linq To Object Query?

I have a query that fails to execute with 'Could not allocate a new page for database 'TEMP… Read more What "clustered Index Scan (clustered)" Means On Sql Server Execution Plan?

If one writes query Q in a relational DBMS, won't the optimizer choose the best way to execute … Read more Dbms Optimizer - Best Execution Plan, No Matter The Query's Formulation

I have two tables in my database users and articles. Records in my users and articles table are giv… Read more Why Does Mysql Not Always Use Index For Select Query?

Consider the following queries. select * from contact where firstname like '%some%' select… Read more Adding Inner Query Is Not Changing The Execution Plan

I want to know how the optimizer rewrote the query and how to read the execution plan in PostgreSQL… Read more In Postgresql What Does Hashed Subplan Mean?

I am calling SQL Server 10 from Entity Framework in C# and want to get a query hint into the reques… Read more Force Hint To Index From Entity Framework To Sql Server

As I know, heap tables are tables without clustered index and has no physical order. I have a heap… Read more Why Nonclustered Index Scan Faster Than Clustered Index Scan?