Application Development Guide

Embedding SQL Statements in C and C++

Embedded SQL statements consist of the following three elements:

Element

Correct Syntax

Statement initializer

EXEC SQL

Statement string

Any valid SQL statement

Statement terminator

semicolon (;)

For example:

     EXEC SQL SELECT col INTO :hostvar FROM table;

The following rules apply to embedded SQL statements:

• You can begin the SQL statement string on the same line as the keyword pair or a separate line. The statement string can be several lines long. Do not split the EXEC SQL keyword pair between lines.
• You must use the SQL statement terminator. If you do not use it, the precompiler will continue to the next terminator in the application. This may cause indeterminate errors.

  C/C++ comments can be placed before the statement initializer or after the statement terminator.

• Multiple SQL statements and C/C++ statements may be placed on the same line. For example:

       EXEC SQL OPEN c1; if (SQLCODE >= 0) EXEC SQL FETCH c1 INTO :hv; 
  

• The SQL precompiler leaves CR/LFs and TABs in a quoted string as is.
• SQL comments are allowed on any line that is part of an embedded SQL statement. These comments are not allowed in dynamically executed statements. The format for an SQL comment is a double dash (--) followed by a string of zero or more characters and terminated by a line end. Do not place SQL comments after the SQL statement terminator as they will cause compilation errors because they would appear to be part of the C/C++ language.

  You can use comments in a static statement string wherever blanks are allowed. Use the C/C++ comment delimiters /* */, or the SQL comment symbol (--). //-style C++ comments are not permitted within static SQL statements, but they may be used elsewhere in your program. The precompiler removes comments before processing the SQL statement. You cannot use the C and C++ comment delimiters /* */ or // in a dynamic SQL statement. However, you can use them elsewhere in your program.

• You can continue SQL string literals and delimited identifiers over line breaks in C and C++ applications. To do this, use a back slash (\) at the end of the line where the break is desired. For example:

       EXEC SQL SELECT "NA\ 
       ME" INTO :n FROM staff WHERE name='Sa\ 
       nders'; 
  

  Any new line characters (such as carriage return and line feed) are not included in the string or delimited identifier.

• Substitution of white space characters such as end-of-line and TAB characters occur as follows:
  • When they occur outside quotation marks (but inside SQL statements), end-of-lines and TABs are substituted by a single space.
  • When they occur inside quotation marks, the end-of-line characters disappear, provided the string is continued properly for a C program. TABs are not modified.

  Note that the actual characters used for end-of-line and TAB vary from platform to platform. For example, OS/2 uses Carriage Return/Line Feed for end-of-line, whereas UNIX-based systems use just a Line Feed.