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SQL Anywhere 12.0.0 (Français) » UltraLite - C and C++ Programming » Application development » Developing applications using embedded SQL » Using host variables » Using indicator variables


Using indicator variables to handle NULL

Do not confuse the SQL concept of NULL with the C-language constant of the same name. In the SQL language, NULL represents either an unknown attribute or inapplicable information. The C-language constant represents a pointer value that does not point to a memory location.

When NULL is used in the SQL Anywhere documentation, it refers to the SQL database meaning given above. The C language constant is referred to as the null pointer (lowercase).

NULL is not the same as any value of the column's defined type. To pass NULL values to the database or receive NULL results back, you require something beyond regular host variables. Indicator variables serve this purpose.

 Using indicator variables when inserting NULL
 Using indicator variables when fetching NULL