GUI Query Builder - Where Tab

Access this window from the Where tab of the Query Builder.

This window is used to build the Where Clauses comprising a Where Statement. The Where statement specifies which rows will be returned by the query.

Where Statements

A Where Statement consists of a number Where clauses, connected by ANDs and ORs; and indented within various levels of brackets

For instance, the following Where Statement consists of 4 Where Clauses

(name=’fred’ and state=’CA’) or (salary<10000 and name is null)

When you go the Where tab, you will be shown the individual Where clauses in your query.

Building a Where Statement

You build your Where statement in two steps:

• build the individual Where Clauses by clicking on New. This will take you to the Build Where Clause window.
• specify how the Where clauses are connected by specifying the Operator (AND/OR) and the bracketting

Understanding AND / OR

People new to SQL can sometimes be confused about the meaning of AND and OR as they can appear to have a different meaning to ordinary speach.

• name=’fred’ AND state=’CA’ means "show all rows which have name='fred' and also have state='CA'".
• name=’fred’ OR state=’CA’ means "show all rows which have name='fred' or have state='CA'".

So

• AND makes the query more restrictive, so you will generally get less rows
• OR makes the query less restrictive, so you will generally get more rows

Show Clauses as Numbers

When you have a complex Where Statement, it can be difficult to visualize how the clauses connect. In this case it can be useful to select Show Clauses as Numbers. When this is done, the Where statement is shown in the following format - this can be make it easier to interpret.

Disabling a Where Clause

You can disable a Where clause by checking the Disable check box.

This "removes" the Where Clause from the query, however it will remain in the grid and can easily be added back in.

Show What

If you are building a Summary Query, you will get another box:

This specifies whether the grid is to show your Where Statement or your Having Statement. This is discussed in Having Statement