27.7.6.17 mysql_fetch_field()
MYSQL_FIELD *mysql_fetch_field(MYSQL_RES *result)
Returns the definition of one column of a result set as a MYSQL_FIELD
structure. Call this function repeatedly to retrieve information about all columns in the result set. mysql_fetch_field()
returns NULL
when no more fields are left.
mysql_fetch_field()
is reset to return information about the first field each time you execute a new SELECT
query. The field returned by mysql_fetch_field()
is also affected by calls to mysql_field_seek()
.
If you've called mysql_query()
to perform a SELECT
on a table but have not called mysql_store_result()
, MySQL returns the default blob length (8KB) if you call mysql_fetch_field()
to ask for the length of a BLOB
field. (The 8KB size is chosen because MySQL does not know the maximum length for the BLOB
. This should be made configurable sometime.) Once you've retrieved the result set, field->max_length
contains the length of the largest value for this column in the specific query.