SQL SECTION

What is SQL SECTION in Embedded SQL?

Marks the start and end of a host-variable declaration block in embedded SQL.

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Compatible dialects for SQL SECTION: Oracle (Pro*C, Pro*COBOL), PostgreSQL (ecpg), IBM Db2, Informix ESQL/C, SAP ASE, Teradata Preprocessor2

SQL SECTION Full Explanation

SQL SECTION is part of the Embedded SQL standard (ISO/IEC 9075-2). It appears only inside EXEC SQL statements and is used to declare host variables that a host language (C, C++, COBOL, etc.) can pass to and from the database. The block is delimited by EXEC SQL BEGIN DECLARE SECTION; and EXEC SQL END DECLARE SECTION;. Everything between those two statements is treated by the pre-compiler as host-language code whose variables become usable in subsequent embedded SQL commands. The SECTION keyword itself does not execute at runtime; it guides the pre-compiler. Omitting it or mis-pairing BEGIN and END leads to compilation errors. SECTION is mandatory when you want to use host variables without explicitly prefixing each one with a host indicator (for example, :var in Pro*C).

SQL SECTION Syntax

EXEC SQL BEGIN DECLARE SECTION;
/* host-language variable declarations */
EXEC SQL END DECLARE SECTION;

SQL SECTION Parameters

Example Queries Using SQL SECTION

EXEC SQL BEGIN DECLARE SECTION;
    int   user_id;
    char  user_email[255];
EXEC SQL END DECLARE SECTION;

/* later in the program */
EXEC SQL SELECT email INTO :user_email FROM users WHERE id = :user_id;

Expected Output Using SQL SECTION

The pre-compiler registers user_id and user_email as host variables
At runtime the SELECT copies the email column into user_email

Use Cases with SQL SECTION

Declaring C variables that will hold query results
Passing COBOL variables into INSERT or UPDATE statements
Grouping multiple host-language declarations in one place for clarity
Ensuring portable embedded SQL across databases that implement ISO standards

Common Mistakes with SQL SECTION

Forgetting EXEC SQL keywords (BEGIN DECLARE SECTION alone is invalid)
Omitting the matching END DECLARE SECTION
Placing executable SQL inside the DECLARE SECTION block
Attempting to use SECTION outside an embedded SQL pre-compiler

First Introduced In

SQL-92 Embedded SQL (ISO/IEC 9075-2:1992)

Frequently Asked Questions

What languages can use SQL SECTION?

C, C++, COBOL, and other languages that have an Embedded SQL pre-compiler compatible with ISO/IEC 9075-2.

Can I nest DECLARE SECTION blocks?

Most pre-compilers do not allow nesting. Use one BEGIN/END pair per compilation unit.

Is SECTION required for every host variable?

If your pre-compiler supports the :host_var syntax outside SECTION blocks, you can omit it, but using SECTION improves readability and portability.

Does SQL SECTION affect runtime performance?

No. It is a compile-time directive only; it has zero runtime cost.