Force Keywords in Select Statements

Hi,

Can anyone explain for me whats the meaning of the words as per below

1). forcePlaceholders

2). forceSelectOrder

3). forceNestedLoop

  1. forceliterals

Regards

AK

ForcePlaceholders

ForcePlaceholders instructs the kernel not to reveal the actual values used in

“where” clauses to the database server at the time of optimization. This is the

default in all non-join statements. The advantage of using this keyword is that the

kernel can reuse the access plan for other similar statements with other search

values. The disadvantage is that the access plan is computed without considering

that data distribution might not be even, or that the access plan is an “on average”

access plan

ForceLiterals

ForceLiterals instructs the kernel to reveal the actual values used in the “where”

clauses to the database server at the time of optimization

ForceSelectOrder

This keyword forces the database server to access the tables in a join in the given

order. If two tables are joined the first table in the statement is always accessed

first. This keyword is frequently combined with the “forceNestedLoop” keyword.

ForceNestedLoops

This keyword forces the database server to use a nested-loop algorithm to process

a given SQL statement that contains a join. This means that a record from the

first table is fetched before trying to fetch any records from the second table.

Generally other join algorithms like hash-joins, merge-joins, and others are also

considered. This keyword is frequently combined with the “forceSelectOrder”

keyword.

And Atul for more Information opn this you can refer DEV 3, Chp - 2, In Ms Dynamics Ax 2009: Development Introduction.

Hope this information will help you… :slight_smile:

Thanks Jasmine…[:)]