使用Perl/DBI/MySQL/InnoDB查找外鍵信息

Question

我想以編程方式在我的MySQL數據庫的特定InnoDB表上找到外鍵。

我正在使用Perl，並且偶然發現了$dbh->foreign_key_info。我剛剛嘗試過使用它，但似乎有點錯誤。

它不返回ON DELETE和ON UPDATE信息，即使它暗示它可以。它也會返回常規索引。

感謝您的任何幫助。

use strict; 
use warnings; 
use DBI; 
use Data::Dumper; 
my $dbh = DBI->connect("DBI:mysql:database=db;host=localhost", "user", "password"); 
my $sth = $dbh->foreign_key_info(undef, undef, undef, undef, undef, "table_name"); 
print Dumper $sth->fetchall_hashref("FK_NAME"); 

和輸出：

$VAR1 = { 
     'some_table_ibfk_3' => { 
            'PK_NAME' => undef, 
            'DEFERABILITY' => undef, 
            'FKTABLE_CAT' => undef, 
            'PKTABLE_SCHEM' => 'db', 
            'UNIQUE_OR_PRIMARY' => undef, 
            'PKTABLE_CAT' => undef, 
            'FKTABLE_NAME' => 'some_table', 
            'FKTABLE_SCHEM' => 'db', 
            'PKTABLE_NAME' => 'some_other_table', 
            'FKCOLUMN_NAME' => 'some_other_table_id', 
            'FK_NAME' => 'some_table_ibfk_3', 
            'DELETE_RULE' => undef, 
            'PKCOLUMN_NAME' => 'id', 
            'KEY_SEQ' => '1', 
            'UPDATE_RULE' => undef 
            }, 
     'user_id_2' => { 
         'PK_NAME' => undef, 
         'DEFERABILITY' => undef, 
         'FKTABLE_CAT' => undef, 
         'PKTABLE_SCHEM' => undef, 
         'UNIQUE_OR_PRIMARY' => undef, 
         'PKTABLE_CAT' => undef, 
         'FKTABLE_NAME' => 'some_table', 
         'FKTABLE_SCHEM' => 'db', 
         'PKTABLE_NAME' => undef, 
         'FKCOLUMN_NAME' => 'some_other_table_id', 
         'FK_NAME' => 'user_id_2', 
         'DELETE_RULE' => undef, 
         'PKCOLUMN_NAME' => undef, 
         'KEY_SEQ' => '2', 
         'UPDATE_RULE' => undef 
        }, 
     'PRIMARY' => { 
        'PK_NAME' => undef, 
        'DEFERABILITY' => undef, 
        'FKTABLE_CAT' => undef, 
        'PKTABLE_SCHEM' => undef, 
        'UNIQUE_OR_PRIMARY' => undef, 
        'PKTABLE_CAT' => undef, 
        'FKTABLE_NAME' => 'some_table', 
        'FKTABLE_SCHEM' => 'db', 
        'PKTABLE_NAME' => undef, 
        'FKCOLUMN_NAME' => 'id', 
        'FK_NAME' => 'PRIMARY', 
        'DELETE_RULE' => undef, 
        'PKCOLUMN_NAME' => undef, 
        'KEY_SEQ' => '1', 
        'UPDATE_RULE' => undef 
        }, 
     'some_table_ibfk_1' => { 
            'PK_NAME' => undef, 
            'DEFERABILITY' => undef, 
            'FKTABLE_CAT' => undef, 
            'PKTABLE_SCHEM' => 'db', 
            'UNIQUE_OR_PRIMARY' => undef, 
            'PKTABLE_CAT' => undef, 
            'FKTABLE_NAME' => 'some_table', 
            'FKTABLE_SCHEM' => 'db', 
            'PKTABLE_NAME' => 'user_bk2', 
            'FKCOLUMN_NAME' => 'user_id', 
            'FK_NAME' => 'some_table_ibfk_1', 
            'DELETE_RULE' => undef, 
            'PKCOLUMN_NAME' => 'id', 
            'KEY_SEQ' => '1', 
            'UPDATE_RULE' => undef 
            }, 
     'some_table_ibfk_2' => { 
            'PK_NAME' => undef, 
            'DEFERABILITY' => undef, 
            'FKTABLE_CAT' => undef, 
            'PKTABLE_SCHEM' => 'db', 
            'UNIQUE_OR_PRIMARY' => undef, 
            'PKTABLE_CAT' => undef, 
            'FKTABLE_NAME' => 'some_table', 
            'FKTABLE_SCHEM' => 'db', 
            'PKTABLE_NAME' => 'user_bk2', 
            'FKCOLUMN_NAME' => 'coach_id', 
            'FK_NAME' => 'some_table_ibfk_2', 
            'DELETE_RULE' => undef, 
            'PKCOLUMN_NAME' => 'id', 
            'KEY_SEQ' => '1', 
            'UPDATE_RULE' => undef 
            } 
    }; 

Answer 1

看起來它可能不被MySQL驅動程序被支持。通過調試做一個快速檢查，它看起來像下面的SQL語句被進入：

SELECT NULL AS PKTABLE_CAT, 
    A.REFERENCED_TABLE_SCHEMA AS PKTABLE_SCHEM, 
    A.REFERENCED_TABLE_NAME AS PKTABLE_NAME, 
    A.REFERENCED_COLUMN_NAME AS PKCOLUMN_NAME, 
    A.TABLE_CATALOG AS FKTABLE_CAT, 
    A.TABLE_SCHEMA AS FKTABLE_SCHEM, 
    A.TABLE_NAME AS FKTABLE_NAME, 
    A.COLUMN_NAME AS FKCOLUMN_NAME, 
    A.ORDINAL_POSITION AS KEY_SEQ, 
    NULL AS UPDATE_RULE, 
    NULL AS DELETE_RULE, 
    A.CONSTRAINT_NAME AS FK_NAME, 
    NULL AS PK_NAME, 
    NULL AS DEFERABILITY, 
    NULL AS UNIQUE_OR_PRIMARY 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE A, 
    INFORMATION_SCHEMA.TABLE_CONSTRAINTS B 
WHERE A.TABLE_SCHEMA = B.TABLE_SCHEMA AND A.TABLE_NAME = B.TABLE_NAME 
    AND A.CONSTRAINT_NAME = B.CONSTRAINT_NAME AND B.CONSTRAINT_TYPE IS NOT NULL 
    AND A.TABLE_NAME = ? ORDER BY A.TABLE_SCHEMA, A.TABLE_NAME, A.ORDINAL_POSITION 

注意，UPDATE_RULE和DELETE_RULE列都被設置爲NULL。