MYSQL

This structure represents a handle to one database connection. It is used for almost all MySQL functions. You should not try to make a copy of a MYSQL structure. There is no guarantee that such a copy will be usable.

MYSQL_RES

This structure represents the result of a query that returns rows (SELECT, SHOW, DESCRIBE, EXPLAIN). The information returned from a query is called the result set in the remainder of this section.

MYSQL_ROW

This is a type-safe representation of one row of data. It is currently implemented as an array of counted byte strings. (You cannot treat these as null-terminated strings if field values may contain binary data, because such values may contain null bytes internally.) Rows are obtained by calling mysql_fetch_row().

MYSQL_FIELD

This structure contains information about a field, such as the field's name, type, and size. Its members are described in more detail here. You may obtain the MYSQL_FIELD structures for each field by calling mysql_fetch_field() repeatedly. Field values are not part of this structure; they are contained in a MYSQL_ROW structure.

MYSQL_FIELD_OFFSET

This is a type-safe representation of an offset into a MySQL field list. (Used by mysql_field_seek().) Offsets are field numbers within a row, beginning at zero.

my_ulonglong

The type used for the number of rows and for mysql_affected_rows(), mysql_num_rows(), and mysql_insert_id(). This type provides a range of 0 to 1.84e19.

On some systems, attempting to print a value of type my_ulonglong does not work. To print such a value, convert it to unsigned long and use a %lu print format. Example:

printf ("Number of rows: %lu\n", (unsigned long) mysql_num_rows(result));

char * name

The name of the field, as a null-terminated string. If the field was given an alias with an AS clause, the value of name is the alias.

char * org_name

The name of the field, as a null-terminated string. Aliases are ignored.

char * table

The name of the table containing this field, if it isn't a calculated field. For calculated fields, the table value is an empty string. If the table was given an alias with an AS clause, the value of table is the alias.

char * org_table

The name of the table, as a null-terminated string. Aliases are ignored.

char * db

The name of the database that the field comes from, as a null-terminated string. If the field is a calculated field, db is an empty string.

char * catalog

The catalog name. This value is always "def".

char * def

The default value of this field, as a null-terminated string. This is set only if you use mysql_list_fields().

unsigned long length

The width of the field, as specified in the table definition.

unsigned long max_length

The maximum width of the field for the result set (the length of the longest field value for the rows actually in the result set). If you use mysql_store_result() or mysql_list_fields(), this contains the maximum length for the field. If you use mysql_use_result(), the value of this variable is zero.

unsigned int name_length

The length of name.

unsigned int org_name_length

The length of org_name.

unsigned int table_length

The length of table.

unsigned int org_table_length

The length of org_table.

unsigned int db_length

The length of db.

unsigned int catalog_length

The length of catalog.

unsigned int def_length

The length of def.

unsigned int flags

Different bit-flags for the field. The flags value may have zero or more of the following bits set:

Use of the BLOB_FLAG, ENUM_FLAG, SET_FLAG, and TIMESTAMP_FLAG flags is deprecated because they indicate the type of a field rather than an attribute of its type. It is preferable to test field->type against MYSQL_TYPE_BLOB, MYSQL_TYPE_ENUM, MYSQL_TYPE_SET, or MYSQL_TYPE_TIMESTAMP instead.

The following example illustrates a typical use of the flags value:

if (field->flags & NOT_NULL_FLAG)
    printf("Field can't be null\n");

You may use the following convenience macros to determine the boolean status of the flags value:

unsigned int decimals

The number of decimals for numeric fields.

unsigned int charset_nr

The character set number for the field.

enum enum_field_types type

The type of the field. The type value may be one of the MYSQL_TYPE_ symbols shown in the following table.

You can use the IS_NUM() macro to test whether a field has a numeric type. Pass the type value to IS_NUM() and it evaluates to TRUE if the field is numeric:

if (IS_NUM(field->type))
    printf("Field is numeric\n");