MySQL :: MySQL 8.4 C API Developer Guide :: 5.4.47 mysql_list_fields() (original) (raw)

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5.4.47 mysql_list_fields()

MYSQL_RES *
mysql_list_fields(MYSQL *mysql,
                  const char *table,
                  const char *wild)

Description

Returns an empty result set for which the metadata provides information about the columns in the given table that match the simple regular expression specified by thewild parameter. wild may contain the wildcard characters % or_, or may be a NULL pointer to match all fields. Callingmysql_list_fields() is similar to executing the query SHOW COLUMNS FROM_`tblname`_ [LIKE_`wild`_].

The information obtained is roughly equivalent to that produced by executing the statement shown here using themysql client, like this:

$> mysql test --column-type-info -e "SELECT * FROM t LIMIT 0"
Field   1:  `c1`
Catalog:    `def`
Database:   `test`
Table:      `t`
Org_table:  `t`
Type:       LONG
Collation:  binary (63)
Length:     11
Max_length: 0
Decimals:   0
Flags:      NUM 

Field   2:  `c2`
Catalog:    `def`
Database:   `test`
Table:      `t`
Org_table:  `t`
Type:       LONG
Collation:  binary (63)
Length:     11
Max_length: 0
Decimals:   0
Flags:      NUM 

$>

It is preferable to use SHOW COLUMNS FROM_`tblname`_ instead ofmysql_list_fields().

You must free the result set withmysql_free_result().

Return Values

A MYSQL_RES result set for success.NULL if an error occurred.

Errors

• CR_COMMANDS_OUT_OF_SYNC
  Commands were executed in an improper order.
• CR_SERVER_GONE_ERROR
  The MySQL server has gone away.
• CR_SERVER_LOST
  The connection to the server was lost during the query.
• CR_UNKNOWN_ERROR
  An unknown error occurred.

Example

int i;
MYSQL_RES *tbl_cols = mysql_list_fields(mysql, "mytbl", "f%");

unsigned int field_cnt = mysql_num_fields(tbl_cols);
printf("Number of columns: %d\n", field_cnt);

for (i=0; i < field_cnt; ++i)
{
  /* col describes i-th column of the table */
  MYSQL_FIELD *col = mysql_fetch_field_direct(tbl_cols, i);
  printf ("Column %d: %s\n", i, col->name);
}
mysql_free_result(tbl_cols);