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mysql> SHOW INDEX FROM tb_stu_info2\G
1. row
Table: tb_stu_info2
Non_unique: 0
Key_name: height
Seq_in_index: 1
Column_name: height
Collation: A
Cardinality: 0
Sub_part: NULL
Packed: NULL
Null: YES
Index_type: BTREE
Comment:
Index_comment:
1 row in set (0.03 sec)
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Table 表示å建索å¼çæ°æ®è¡¨åï¼è¿éæ¯ tb_stu_info2 æ°æ®è¡¨ã
Non_unique 表示该索å¼æ¯å¦æ¯å¯ä¸ç´¢å¼ãè¥ä¸æ¯å¯ä¸ç´¢å¼ï¼å该åçå¼ä¸º 1ï¼è¥æ¯å¯ä¸ç´¢å¼ï¼å该åçå¼ä¸º 0ã
Key_name 表示索å¼çå称ã
Seq_in_index 表示该åå¨ç´¢å¼ä¸çä½ç½®ï¼å¦æç´¢å¼æ¯ååçï¼å该åçå¼ä¸º 1ï¼å¦æç´¢å¼æ¯ç»åç´¢å¼ï¼å该åçå¼ä¸ºæ¯åå¨ç´¢å¼å®ä¹ä¸ç顺åºã
Column_name 表示å®ä¹ç´¢å¼çåå段ã
Collation 表示å以ä½ç§é¡ºåºåå¨å¨ç´¢å¼ä¸ãå¨ MySQL ä¸ï¼ååºæ¾ç¤ºå¼âAâï¼ååºï¼ï¼è¥æ¾ç¤ºä¸º NULLï¼å表示æ åç±»ã
Cardinality ç´¢å¼ä¸å¯ä¸å¼æ°ç®ç估计å¼ãåºæ°æ ¹æ®è¢«åå¨ä¸ºæ´æ°çç»è®¡æ°æ®è®¡æ°ï¼æ以å³ä½¿å¯¹äºå°å表ï¼è¯¥å¼ä¹æ²¡æå¿
è¦æ¯ç²¾ç¡®çãåºæ°è¶å¤§ï¼å½è¿è¡èåæ¶ï¼MySQL 使ç¨è¯¥ç´¢å¼çæºä¼å°±è¶å¤§ã
Sub_part 表示åä¸è¢«ç¼å
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Packed æ示å
³é®åå¦ä½è¢«å缩ãè¥æ²¡æ被å缩ï¼å¼ä¸º NULLã
Null ç¨äºæ¾ç¤ºç´¢å¼åä¸æ¯å¦å
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Index_type æ¾ç¤ºç´¢å¼ä½¿ç¨çç±»ååæ¹æ³ï¼BTREEãFULLTEXTãHASHãRTREEï¼ã
Comment æ¾ç¤ºè¯æ³¨ã
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