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SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
Guide to SQL: Syntax
The Informix® Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the Informix dialect of the SQL language.
SPL statements
These topics describe Stored Procedure Language (SPL) statements, which you use to write SPL routines. You can store these routines in the database as user-defined routines (UDRs).
LET

SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
- Guide to SQL: Syntax
  The Informix® Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the Informix dialect of the SQL language.
  - Overview of SQL syntax
    These topics provide an overview about how to use the SQL statements, SPL statements, and syntax segments.
  - SQL statements
    This chapter describes the syntax and semantics of SQL statements that are recognized by Informix®.
  - SPL statements
    These topics describe Stored Procedure Language (SPL) statements, which you use to write SPL routines. You can store these routines in the database as user-defined routines (UDRs).
    - << Label >> statement
      Use the <<label>> statement of SPL to declare a statement label or a loop label.
    - CALL
    - CASE
      Use the CASE statement when program execution needs to take exactly one among multiple branches, depending on the value of an SPL variable or of a simple expression. The CASE statement is a logical alternative to the IF statement.
    - CONTINUE
    - DEFINE
    - EXIT
    - FOR
    - FOREACH
      Use the FOREACH statement to declare a direct cursor that can select and manipulate more than one row from a the result set of a query, or more than one element from a collection.
    - GOTO
    - IF
    - LET
      - Using a SELECT Statement in a LET Statement
      - Calling a Function in a LET Statement
    - LOOP
    - ON EXCEPTION
    - RAISE EXCEPTION
    - RETURN
    - SYSTEM
    - TRACE
    - WHILE
      Use the WHILE statement to establish a loop with variable end conditions.
  - Data types and expressions
    These topics describe the data types and expressions that Informix®supports.
  - Other syntax segments
    These topics describe syntax segments, which are language elements, such as database object names or optimizer directives, that appear as a subdiagram reference in the syntax diagrams of some SQL or SPL statements.
  - Built-In Routines
  - Appendixes
- Guide to SQL: Reference
  The Informix® Guide to SQL: Reference contains the reference information for the system catalog tables, data types, and environment variables of the HCL Informix dialect of the SQL language, as implemented in HCL Informix. These topics also include information about the stores_demo, sales_demo, and superstore_demo databases that are included with HCL Informix.
- Guide to SQL: Tutorial
  The Informix® Guide to SQL: Tutorial shows how to use basic and advanced structured query language (SQL) to access and manipulate the data in your databases. It discusses the data manipulation language (DML) statements as well as triggers and stored procedure language (SPL) routines, which DML statements often use.

LET

Use the LET statement to assign values to variables or to call a user-defined SPL routine and assign the returned value or values to SPL variables.

Syntax

^{(explicit id let002)
let002} ^{(explicit id let003)
let003} ^{(explicit id let004)
let004} LET SPL_var = { | function( [ <Argument>^[] ] ) | <Expression>^[] | ( <SELECT Statement>^[] ) } ;


Element	Description	Restrictions	Syntax
function	SPL function to be invoked	Must exist in the database	Identifier
SPL_var	SPL variable to receive a value that the function, expression, or query returns	Must be defined and in scope within the statement block	Identifier;

Usage

The LET statement can assign a value returned by an expression, function, or query to an SPL variable. At runtime, the value to be assigned is calculated first. The resulting value is cast to the data type of SPL_var, if possible, and the assignment occurs. If conversion is not possible, an error occurs, and the value of the variable remains undefined. (A LET operation that assigns a single value to a single SPL variable is called a simple assignment.)

A compound assignment assigns multiple expressions to multiple SPL variables. The data types of expressions in the expression list do not need to match the data types of the corresponding variables in the variable list, because the database server automatically converts the data types. (For a detailed discussion of casting, see the Informix® Guide to SQL: Reference.)

In multiple-assignment operations, the number of variables to the left of the equal ( = ) sign must match the number of values returned by the functions, expressions, and queries listed on the right of the equal ( = ) sign. The following example shows several LET statements that assign values to SPL variables:

LET a   = c + d ;
LET a,b = c,d ;
LET expire_dt = end_dt + 7 UNITS DAY; 
LET name = 'Brunhilda';
LET sname = DBSERVERNAME;
LET this_day = TODAY;

You cannot use multiple values to the right of the equal ( = ) sign to operate on other values. For example, the following statement is not valid:

LET a,b = (c,d) + (10,15); -- INVALID EXPRESSION

¹ See Arguments

² See Expression

³ See SELECT statement