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## SQLite C Interface

### Extract Metadata About A Column Of A Table

>     int sqlite3_table_column_metadata(
>       sqlite3 *db,                /* Connection handle */
>       const char *zDbName,        /* Database name or NULL */
>       const char *zTableName,     /* Table name */
>       const char *zColumnName,    /* Column name */
>       char const **pzDataType,    /* OUTPUT: Declared data type */
>       char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
>       int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
>       int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
>       int *pAutoinc               /* OUTPUT: True if column is auto-increment */
>     );

This routine returns meta-data about a specific column of a specific database table accessible using the connection handle passed as the first function argument.

The column is identified by the second, third and fourth parameters to this function. The second parameter is either the name of the database (i.e. "main", "temp" or an attached database) containing the specified table or NULL. If it is NULL, then all attached databases are searched for the table using the same algorithm as the database engine uses to resolve unqualified table references.

The third and fourth parameters to this function are the table and column name of the desired column, respectively. Neither of these parameters may be NULL.

Meta information is returned by writing to the memory locations passed as the 5th and subsequent parameters to this function. Any of these arguments may be NULL, in which case the corresponding element of meta information is ommitted.

    Parameter     Output Type      Description
    -----------------------------------

    5th         const char*      Data type
    6th         const char*      Name of the default collation sequence
    7th         int              True if the column has a NOT NULL constraint
    8th         int              True if the column is part of the PRIMARY KEY
    9th         int              True if the column is AUTOINCREMENT

The memory pointed to by the character pointers returned for the declaration type and collation sequence is valid only until the next call to any sqlite API function.

If the specified table is actually a view, then an error is returned.

If the specified column is "rowid", "oid" or "_rowid_" and an INTEGER PRIMARY KEY column has been explicitly declared, then the output parameters are set for the explicitly declared column. If there is no explicitly declared IPK column, then the output parameters are set as follows:

    data type: "INTEGER"
    collation sequence: "BINARY"
    not null: 0
    primary key: 1
    auto increment: 0

This function may load one or more schemas from database files. If an error occurs during this process, or if the requested table or column cannot be found, an SQLITE error code is returned and an error message left in the database handle (to be retrieved using sqlite3_errmsg()).

This API is only available if the library was compiled with the SQLITE_ENABLE_COLUMN_METADATA preprocessor symbol defined.

See also lists of Objects, Constants, and Functions.

This page last modified 2007/12/14 14:37:57 UTC