|PostgreSQL Reference Manual - Volume 2 - Programming Guide|
by The PostgreSQL Global Development Group
Paperback (6"x9"), 408 pages
RRP £19.95 ($34.95)
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3.6.2 Declare Sections
To pass data from the program to the database, for example as parameters in a query, or to pass data from the database back to the program, the C variables that are intended to contain this data need to be declared in specially marked sections, so the embedded SQL preprocessor is made aware of them.
This section starts with
EXEC SQL BEGIN DECLARE SECTION;
and ends with
EXEC SQL END DECLARE SECTION;
Between those lines, there must be normal C variable declarations, such as
int x = 4; char foo, bar;
As you can see, you can optionally assign an initial value to the variable. The variable's scope is determined by the location of its declaring section within the program. You can also declare variables with the following syntax which implicitly creates a declare section:
EXEC SQL int i = 4;
You can have as many declare sections in a program as you like.
The declarations are also echoed to the output file as normal C variables, so there's no need to declare them again. Variables that are not intended to be used in SQL commands can be declared normally outside these special sections.
The definition of a structure or union also must be listed inside
DECLARE section. Otherwise the preprocessor cannot
handle these types since it does not know the definition.
|ISBN 0954612035||PostgreSQL Reference Manual - Volume 2 - Programming Guide||See the print edition|