{"id":134,"title":"\u5916\u952e\u7ea6\u675f","good":0,"bad":0,"hit":1572,"created_at":"2014-12-22 11:50:42","content":"

\u5916\u952e\u7ea6\u675f<\/p>

\u7ea6\u675f\u7684\u4f5c\u7528\uff0c\u662f\u7528\u4e8e\u4fdd\u8bc1\u6570\u636e\u7684\u5b8c\u6574\u6027\u6216\u8005\u5408\u7406\u6027\u7684\u5de5\u5177!<\/p>

\u5916\u952e\uff1aforeign key\uff0c\u5f53\u524d\u8868\u5185\uff0c\u6307\u5411\u5176\u4ed6\u8868\u7684\u4e3b\u952e\u7684\u5b57\u6bb5\uff0c\u79f0\u4e4b\u4e3a\u5916\u952e\uff01<\/p>

 <\/p>

\u5916\u952e\u7ea6\u675f\uff1a\u7528\u4e8e\u9650\u5236\u76f8\u5173\u8054\u7684\u8bb0\u5f55\u5728\u903b\u8f91\u4e0a\u4fdd\u8bc1\u5408\u7406\u6027\u7684\u7ea6\u675f\u79f0\u4e4b\u4e3a\u5916\u952e\u7ea6\u675f\uff01<\/p>

 <\/p>

\u7ea6\u675f\uff0c\u4e0d\u662f\u5b57\u6bb5\u3002<\/p>

\u5e94\u8be5\u6ce8\u610f\u7684\u95ee\u9898\uff1a<\/p>

\u5173\u4e8e\uff0c\u5916\u952e\u7ea6\u675f\uff0c\u53ea\u80fd\u5728\u5f53\u524d\u7684mysql\u7684\u7684innodb\u8868\u7c7b\u578b\uff08\u5f15\u64ce\uff09\u4e0b\u624d\u4f1a\u751f\u6548\uff01<\/span><\/p>

 <\/p>

\u589e\u52a0\u5916\u952e<\/p>

alter table \u8868\u540d add constraint \u7ea6\u675f\u7684\u540d\u5b57 foreignkey \u5916\u952e\u7d22\u5f15\u540d\u5b57 (\u5916\u952e\u5b57\u6bb5\u540d) references \u5173\u8054\u8868\u540d (\u5173\u8054\u5b57\u6bb5) [\u64cd\u4f5c]<\/p>

 <\/p>

\u6ce8\u610f\uff1a\u5982\u679c\u5f53\u524d\u7684\u6570\u636e\uff0c\u5df2\u7ecf\u4e0d\u7b26\u5408\u6240\u89c1\u7ea6\u675f\u5173\u8054\uff0c\u5219\u521b\u5efa\u5931\u8d25\uff01<\/p>

 <\/p>

\u5220\u9664\u5916\u952e<\/p>

alter table table_name drop foreign_key\u5916\u952e\u540d\u5b57\uff01<\/p>

 <\/p>

\u53ef\u4ee5\u901a\u8fc7 show create table \u67e5\u770b\u7ea6\u675f\u7684\u540d\u5b57\uff1a <\/p>

 <\/p>

\u6ce8\u610f\uff0c\u5916\u952e\u7ea6\u675f\u4e0e\u7d22\u5f15\u7684\u5173\u7cfb\uff1a <\/p>

\u5982\u679c\u9700\u8981\u5728\u67d0\u4e2a\u5b57\u6bb5\u4e0a\uff0c\u589e\u52a0\u5916\u952e\u7ea6\u675f\uff0c\u90a3\u4e48\u9700\u8981\u8be5\u5b57\u6bb5\u4e5f\u540c\u6837\u6709\u7d22\u5f15\uff01\u5982\u679c\u8be5\u5b57\u6bb5\u4e0a\uff0c\u6ca1\u6709\u7d22\u5f15\uff0c\u6b64\u65f6\uff0cmysql\u4f1a\u81ea\u52a8\u5728\u8be5\u5b57\u6bb5\u4e0a\u589e\u52a0\u4e00\u4e2a\u666e\u901a\u7d22\u5f15\uff01 <\/p>

 <\/p>

\u53ef\u4ee5\u9009\u62e9\u6307\u5b9a\u5916\u952e\u7ea6\u675f\u7684\u540d\u5b57\uff1a<\/p>

\u6ce8\u610f\u4e0a\u9762\u7684\u5916\u952e\u7ea6\u675f\u81ea\u52a8\u5efa\u7acb\u7684\u7d22\u5f15\u7684\u540d\u5b57\uff0c\u4e0e\u5916\u952e\u7684\u540d\u5b57\u76f8\u540c\uff01<\/p>

 <\/p>

\u603b\u7ed3\uff1a\u5728\u521b\u5efa\u65f6\uff1a<\/p>

1\uff0c  \u5916\u952e\u4e0e\u76f8\u5e94\u5173\u8054\u8868\u7684\u4e3b\u952e\u7c7b\u578b<\/p>

2\uff0c  \u5df2\u6709\u6570\u636e\uff0c\u5fc5\u987b\u6ee1\u8db3\u7ea6\u675f\u6761\u4ef6\u624d\u53ef\u4ee5\uff01<\/p>

3\uff0c  \u53ef\u4ee5\u4f7f\u7528constraint \u5173\u952e\u5b57\uff0c\u4e3a\u5916\u952e\u7ea6\u675f\u8d77\u540d\u5b57\uff01<\/p>

 <\/p>

 <\/p>

\u7ea6\u675f\u64cd\u4f5c<\/p>

\u5728\u5bf9\u7236\u8868\uff08\u88ab\u5173\u8054\u7684\u8868\uff09\u505a\u64cd\u4f5c\u65f6\uff0c\u6709\u4e09\u79cd\u884c\u4e3a\uff1a<\/p>

1\uff0c  \u4e25\u683c\u9650\u5236\uff0c\u62d2\u7edd\u64cd\u4f5c\u3002restrict<\/p>

2\uff0c  \u7f6e null\uff0cset null<\/p>

3\uff0c  \u7ea7\u8054\u64cd\u4f5c\uff0ccascade<\/p>

\u4ee5\u4e0a\u4e09\u4e2a\u884c\u4e3a\u64cd\u4f5c\uff0c\u4f1a\u5728\u4e3b\u8868\u8bb0\u5f55\u88ab\u5220\u9664\u6216\u8005\u66f4\u65b0\u65f6\u88ab\u4f7f\u7528\uff01<\/p>

on delete set null<\/p>

on update cascade<\/p>

 <\/p>

\u66f4\u65b0\u65f6\u7684\u7ea7\u8054\u64cd\u4f5c\uff1a<\/p>

\u53ea\u6709\u5728\u5173\u8054\u8868\u7684\u4e3b\u952e\u53d1\u751f\u53d8\u5316\u65f6\uff0c\u624d\u4f1a\u5f71\u54cd\u5230\u4ece\u8868\u7684\u5173\u8054\u5b57\u6bb5\u7684\u53d8\u5316\uff01 <\/p>

 <\/p>

\u4e3b\u8868\uff1a\u88ab\u5173\u8054\u7684<\/p>

\u4ece\u8868\uff1a\u53d1\u51fa\u5173\u8054\u7684\uff01<\/p>

 <\/p>

\u5916\u952e\uff0c\u7ad9\u5728php\u7a0b\u5e8f\u7684\u89d2\u5ea6\uff0c\u7528\u5230\u7684\u4e0d\u591a\uff01<\/p>

<\/p>

\u4f8b\u5b50\uff1a<\/p>

<\/p>

\u901a\u8fc7\uff1a<\/p>

show create table student;<\/p>

\u67e5\u770b\u5efa\u8868\u8bed\u53e5\uff0c\u53ef\u4ee5\u770b\u5230\u591a\u4e86\u4e00\u4e2a\u5916\u952e<\/p>

<\/p>"}