Extract Metadata About A Column Of A Table

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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 metadata about a specific column of a specific database table accessible using the database 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 used by the database engine 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.

Metadata 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 metadata is omitted.

> Parameter | Output Type | Description
> --- | --- | ---
> 5th | const char* | Data type
> 6th | const char* | Name of default collation sequence
> 7th | int | True if column has a NOT NULL constraint
> 8th | int | True if column is part of the PRIMARY KEY
> 9th | int | True if 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, an error code 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 INTEGER PRIMARY KEY 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 error code is returned and an error message left in the database connection (to be retrieved using sqlite3_errmsg()).

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

See also lists of Objects, Constants, and Functions.