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The PostgreSQL 9.0 Reference Manual - Volume 2 - Programming Guide
by The PostgreSQL Global Development Group
Paperback (6"x9"), 478 pages
ISBN 9781906966065
RRP £14.95 ($19.95)

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3.11.2 sqlca

For more powerful error handling, the embedded SQL interface provides a global variable with the name sqlca that has the following structure:

struct
{
    char sqlcaid[8];
    long sqlabc;
    long sqlcode;
    struct
    {
        int sqlerrml;
        char sqlerrmc[SQLERRMC_LEN];
    } sqlerrm;
    char sqlerrp[8];
    long sqlerrd[6];
    char sqlwarn[8];
    char sqlstate[5];
} sqlca;

(In a multithreaded program, every thread automatically gets its own copy of sqlca. This works similarly to the handling of the standard C global variable errno.)

sqlca covers both warnings and errors. If multiple warnings or errors occur during the execution of a statement, then sqlca will only contain information about the last one.

If no error occurred in the last SQL statement, sqlca.sqlcode will be 0 and sqlca.sqlstate will be "00000". If a warning or error occurred, then sqlca.sqlcode will be negative and sqlca.sqlstate will be different from "00000". A positive sqlca.sqlcode indicates a harmless condition, such as that the last query returned zero rows. sqlcode and sqlstate are two different error code schemes; details appear below.

If the last SQL statement was successful, then sqlca.sqlerrd[1] contains the OID of the processed row, if applicable, and sqlca.sqlerrd[2] contains the number of processed or returned rows, if applicable to the command.

In case of an error or warning, sqlca.sqlerrm.sqlerrmc will contain a string that describes the error. The field sqlca.sqlerrm.sqlerrml contains the length of the error message that is stored in sqlca.sqlerrm.sqlerrmc (the result of strlen(), not really interesting for a C programmer). Note that some messages are too long to fit in the fixed-size sqlerrmc array; they will be truncated.

In case of a warning, sqlca.sqlwarn[2] is set to W. (In all other cases, it is set to something different from W.) If sqlca.sqlwarn[1] is set to W, then a value was truncated when it was stored in a host variable. sqlca.sqlwarn[0] is set to W if any of the other elements are set to indicate a warning.

The fields sqlcaid, sqlcabc, sqlerrp, and the remaining elements of sqlerrd and sqlwarn currently contain no useful information.

The structure sqlca is not defined in the SQL standard, but is implemented in several other SQL database systems. The definitions are similar at the core, but if you want to write portable applications, then you should investigate the different implementations carefully.

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