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Crestron e-control Database Manager SW-DBM

37 •• The Database File Installation & Reference Guide — DOC. 5823

A logical condition is an expression. An expression is a combination of column

names, operators, and values. There are several types of operators that you can use to

define the expression you need.

Arithmetic operators form new numeric values by operating on numbers or columns

that contain numbers. Examples are addition (+), subtraction (-), multiplication (*),

and division (/). They operate on numbers and on columns that contain numbers.

Relational operators compare columns and values. The result of a relational

expression is true (include record in query) or false (exclude record from query).

Examples are equal (=), greater than (>), less than (<), greater than or equal to

(>=), and less than or equal to (<=).

Logical operators manipulate relational expressions to return a value of (include

record in query) or false (exclude record from query). Examples are AND, OR, and

NOT. AND connects two relational expressions; both must be true for the combined

expression to be true. OR connects two relational expressions; at least one must be

true for the combined expression to be true. NOT operates on one relational

expression; it reverses the value from true to false or false to true.

String operators manipulate text strings and columns that contain text values. An

example is concatenation (&) which creates one text string by concatenating two

individual strings.

ListFields

The listFields column identifies the columns that comprise the scroller contents. It is

used to construct the SELECT clause of the SQL request. There number of fields

listed must be equal to (or greater than) the number of columns the scroller is

currently using.

Successive queries require additional sets of list fields to be given, one set per line.

The first field in each set is added to the implicit conditions (to the WHERE clause)

of the next query level.

DataFields

The dataFields column identifies the columns from the picked record to be sent to

the touchscreen. The order of fields is as listed in the datafields field of the

Queries table.

Example: Three fields are listed in datafields. When a record is picked from the list,

the three fields are echoed back to the system using the Data

, Data

, and Data

signals.

However, note that only fields defined by the data filter bit pattern are sent. (See

DataFilter in the Signal Reference for more information.)

SQL

If you know the SQL programming language, you can enter a SELECT command in

this column to be used as the query for selecting records from the table. The query is

taken from this column instead of being constructed from the previously described

columns.

NOTE: Even if you supply your own SELECT command, you must still provide the list of fields to

be displayed in the list in the listFields column and the list of fields to be displayed in the opened

record in dataFields.

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