0準備工做：mysql
先爲劍表添加兩個屬性：屬性(attr)和類型(type)
mysql> ALTER TABLE sword ADD attr VARCHAR(4) NOT NULL; Query OK, 0 rows affected (0.11 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE sword ADD type VARCHAR(8) NOT NULL; Query OK, 0 rows affected (0.08 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> SELECT*FROM sword; +----+--------+-------+------+-------+------+------+ | id | name | atk | hit | crit | attr | type | +----+--------+-------+------+-------+------+------+ | 1 | 黑風 | 10800 | 400 | 400 | | | | 2 | 木藜 | 5400 | 200 | 200 | | | | 3 | 荊戈 | 8020 | 1000 | 10 | | | | 4 | 痕兮 | 8998 | 800 | 999 | | | | 5 | 逐暮 | 100 | 1000 | 10000 | | | | 6 | 風躍 | 9020 | 10 | 10 | | | | 8 | 洛神 | 20020 | 1 | 10 | | | | 9 | 隱鋒 | 8020 | 2000 | 10 | | | +----+--------+-------+------+-------+------+------+ 8 rows in set (0.00 sec)
修改數據：(爲屬性添加值)
mysql> UPDATE sword SET attr='木',type='神界' WHERE name='黑風'; Query OK, 0 rows affected (0.00 sec) Rows matched: 1 Changed: 0 Warnings: 0 mysql> UPDATE sword SET attr='木',type='人界' WHERE name='木藜'; Query OK, 0 rows affected (0.01 sec) Rows matched: 1 Changed: 0 Warnings: 0 mysql> UPDATE sword SET attr='金',type='魔界' WHERE name='荊戈'; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> UPDATE sword SET attr='水',type='道界' WHERE name='痕兮'; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> UPDATE sword SET attr='火',type='鬼界' WHERE name='逐暮'; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> UPDATE sword SET attr='木',type='仙界' WHERE name='風躍'; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> UPDATE sword SET attr='金',type='神界' WHERE name='洛神'; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> UPDATE sword SET attr='土',type='人界' WHERE name='隱鋒'; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT*FROM sword; +----+--------+-------+------+-------+------+--------+ | id | name | atk | hit | crit | attr | type | +----+--------+-------+------+-------+------+--------+ | 1 | 黑風 | 10800 | 400 | 400 | 木 | 神界 | | 2 | 木藜 | 5400 | 200 | 200 | 木 | 人界 | | 3 | 荊戈 | 8020 | 1000 | 10 | 金 | 魔界 | | 4 | 痕兮 | 8998 | 800 | 999 | 水 | 道界 | | 5 | 逐暮 | 100 | 1000 | 10000 | 火 | 鬼界 | | 6 | 風躍 | 9020 | 10 | 10 | 木 | 仙界 | | 8 | 洛神 | 20020 | 1 | 10 | 金 | 神界 | | 9 | 隱鋒 | 8020 | 2000 | 10 | 土 | 人界 | +----+--------+-------+------+-------+------+--------+ 8 rows in set (0.00 sec) 8 rows in set (0.00 sec)
子查詢
出如今其餘SQL語句內的SELECT語句
子查詢必須在()內
增刪改查均可以進行子查詢
返回：標量，行，列或子查詢
1.比較運算符的子查詢(=、>、<、>=、<=、<>、!=、<=>)
- 計算平均攻擊力(四捨五入2位)
mysql> SELECT ROUND(AVG(atk),2) AS '平均攻擊力' FROM sword; +-----------------+ | 平均攻擊力 | +-----------------+ | 8797.25 | +-----------------+ 1 row
- 普通查詢：全部攻擊力格大於平均攻擊力的劍，並降序排序
mysql> SELECT * FROM sword WHERE atk > 5636.36 ORDER BY atk DESC; +----+--------+-------+------+------+------+--------+ | id | name | atk | hit | crit | attr | type | +----+--------+-------+------+------+------+--------+ | 8 | 洛神 | 20020 | 1 | 10 | 金 | 神界 | | 1 | 黑風 | 10800 | 400 | 400 | 木 | 神界 | | 6 | 風躍 | 9020 | 10 | 10 | 木 | 仙界 | | 4 | 痕兮 | 8998 | 800 | 999 | 水 | 道界 | | 3 | 荊戈 | 8020 | 1000 | 10 | 金 | 魔界 | | 9 | 隱鋒 | 8020 | 2000 | 10 | 土 | 人界 | +----+--------+-------+------+------+------+--------+ 6 rows in set (0.00 sec)
- 使用子查詢(也就是將上面兩步簡化爲一步)
mysql> SELECT * FROM sword WHERE atk > -> (SELECT ROUND(AVG(atk),2) AS '平均攻擊力' FROM sword) -> ORDER BY atk DESC; +----+--------+-------+-----+------+------+--------+ | id | name | atk | hit | crit | attr | type | +----+--------+-------+-----+------+------+--------+ | 8 | 洛神 | 20020 | 1 | 10 | 金 | 神界 | | 1 | 黑風 | 10800 | 400 | 400 | 木 | 神界 | | 6 | 風躍 | 9020 | 10 | 10 | 木 | 仙界 | | 4 | 痕兮 | 8998 | 800 | 999 | 水 | 道界 | +----+--------+-------+-----+------+------+--------+ 4 rows in set (0.00 sec)
2.ANY、SOME、ALL、IN
ANY 知足一條便可查詢到 SOME 同ANY ALL 知足全部可查詢到 IN 等價於 = ANY 或 = SOME
查詢類型爲人界的劍攻擊力sql
mysql> SELECT atk FROM sword WHERE type = '人界'; +------+ | atk | +------+ | 5400 | | 8020 | +------+ 2 rows in set (0.00 sec) 2 rows in set (0.00 sec)
查詢攻擊力大於(任意一個：ANY)」人族」的劍名稱，並降序排列
雖然荊戈的攻擊力不大於8020，但大於5400，知足一個就能查詢到spa
mysql> SELECT id,name,atk FROM sword WHERE atk > -> ANY(SELECT atk FROM sword WHERE type = '人界') -> ORDER BY atk DESC; +----+--------+-------+ | id | name | atk | +----+--------+-------+ | 8 | 洛神 | 20020 | | 1 | 黑風 | 10800 | | 6 | 風躍 | 9020 | | 4 | 痕兮 | 8998 | | 3 | 荊戈 | 8020 | | 9 | 隱鋒 | 8020 | +----+--------+-------+ 6 rows in set (0.00 sec)
查詢攻擊力大於(全部：ALL)」人族」的劍名稱，並降序排列
雖然荊戈的攻擊力大於5400，但不大於8020，因此查不到code
mysql> SELECT id,name,atk FROM sword WHERE atk > -> ALL(SELECT atk FROM sword WHERE type = '人界') -> ORDER BY atk DESC; +----+--------+-------+ | id | name | atk | +----+--------+-------+ | 8 | 洛神 | 20020 | | 1 | 黑風 | 10800 | | 6 | 風躍 | 9020 | | 4 | 痕兮 | 8998 | +----+--------+-------+ 4 rows in set (0.00 sec)
查詢任意攻擊力等於」人族」的劍名稱，並降序排列
mysql> SELECT id,name,atk FROM sword WHERE atk IN -> (SELECT atk FROM sword WHERE type = '人界') -> ORDER BY atk DESC; +----+--------+------+ | id | name | atk | +----+--------+------+ | 3 | 荊戈 | 8020 | | 9 | 隱鋒 | 8020 | | 2 | 木藜 | 5400 | +----+--------+------+ 3 rows in set (0.00 sec)
建立類型分類表
- 建表
mysql> CREATE TABLE IF NOT EXISTS sword_type(
-> type_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT, -> type_name VARCHAR(8) -> ); Query OK, 0 rows affected (0.04 sec)
- 用分組查詢查看劍分類：
mysql> SELECT type FROM sword GROUP BY type; +--------+ | type | +--------+ | 人界 | | 仙界 | | 神界 | | 道界 | | 鬼界 | | 魔界 | +--------+ 6 rows in set (0.00 sec)
##### ☆☆☆☆☆將查詢的結果寫入另外一個數據表：
- 根據type的分組，經過sword的type字段，插入到sword_type表中的type_name字段排序
mysql> INSERT sword_type (type_name) SELECT type FROM sword GROUP BY type; Query OK, 6 rows affected (0.00 sec) Records: 6 Duplicates: 0 Warnings: 0 mysql> SELECT*FROM sword_type; +---------+-----------+ | type_id | type_name | +---------+-----------+ | 1 | 人界 | | 2 | 仙界 | | 3 | 神界 | | 4 | 道界 | | 5 | 鬼界 | | 6 | 魔界 | +---------+-----------+ 6 rows in set (0.00 sec)
☆☆☆☆☆
使用type_id更新sword中的數據ci
mysql> UPDATE sword INNER JOIN sword_type -> ON type = type_name -> SET type = type_id ; Query OK, 8 rows affected (0.00 sec) Rows matched: 8 Changed: 8 Warnings: 0 mysql> SELECT*FROM sword; +----+--------+-------+------+-------+------+------+ | id | name | atk | hit | crit | attr | type | +----+--------+-------+------+-------+------+------+ | 1 | 黑風 | 10800 | 400 | 400 | 木 | 3 | | 2 | 木藜 | 5400 | 200 | 200 | 木 | 1 | | 3 | 荊戈 | 8020 | 1000 | 10 | 金 | 6 | | 4 | 痕兮 | 8998 | 800 | 999 | 水 | 4 | | 5 | 逐暮 | 100 | 1000 | 10000 | 火 | 5 | | 6 | 風躍 | 9020 | 10 | 10 | 木 | 2 | | 8 | 洛神 | 20020 | 1 | 10 | 金 | 3 | | 9 | 隱鋒 | 8020 | 2000 | 10 | 土 | 1 | +----+--------+-------+------+-------+------+------+ 8 rows in set (0.00 sec)
經過CREATE…SELECT來建立數據表而且同時寫入記錄
此時字段值必須爲sword中的attrrem
mysql> CREATE TABLE sword_attr ( -> attr_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT, -> attr VARCHAR(4) NOT NULL -> ) SELECT attr FROM sword GROUP BY attr; Query OK, 5 rows affected (0.47 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> SELECT*FROM sword_attr; +---------+------+ | attr_id | attr | +---------+------+ | 1 | 土 | | 2 | 木 | | 3 | 水 | | 4 | 火 | | 5 | 金 | +---------+------+ 5 rows in set (0.00 sec)
若是兩表字段相同，這樣會報錯，需具體指定字段屬於哪張表
- 錯誤：
mysql> UPDATE sword INNER JOIN sword_attr -> ON attr = attr -> SET attr = attr_id; ERROR 1052 (23000): Column 'attr' in field list is ambiguous
- 正確
mysql> UPDATE sword AS s INNER JOIN sword_attr AS a -> ON s.attr = a.attr -> SET s.attr = a.attr_id; Query OK, 8 rows affected (0.00 sec) Rows matched: 8 Changed: 8 Warnings: 0 mysql> SELECT*FROM sword; +----+--------+-------+------+-------+------+------+ | id | name | atk | hit | crit | attr | type | +----+--------+-------+------+-------+------+------+ | 1 | 黑風 | 10800 | 400 | 400 | 2 | 3 | | 2 | 木藜 | 5400 | 200 | 200 | 2 | 1 | | 3 | 荊戈 | 8020 | 1000 | 10 | 5 | 6 | | 4 | 痕兮 | 8998 | 800 | 999 | 3 | 4 | | 5 | 逐暮 | 100 | 1000 | 10000 | 4 | 5 | | 6 | 風躍 | 9020 | 10 | 10 | 2 | 2 | | 8 | 洛神 | 20020 | 1 | 10 | 5 | 3 | | 9 | 隱鋒 | 8020 | 2000 | 10 | 1 | 1 | +----+--------+-------+------+-------+------+------+ 8 rows in set (0.00 sec)
查看一下表信息：
mysql> DESC sword; +-------+----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+----------------------+------+-----+---------+----------------+ | id | smallint(5) unsigned | NO | PRI | NULL | auto_increment | | name | varchar(32) | NO | | NULL | | | atk | smallint(5) unsigned | NO | | NULL | | | hit | smallint(5) unsigned | NO | | NULL | | | crit | smallint(5) unsigned | YES | | 10 | | | attr | varchar(4) | NO | | NULL | | | type | varchar(8) | NO | | NULL | | +-------+----------------------+------+-----+---------+----------------+ 7 rows in set (0.00 sec)
此時能夠改attr和type的類型爲數字，it
mysql> ALTER TABLE sword -> CHANGE type type_id SMALLINT UNSIGNED NOT NULL, -> CHANGE attr attr_id SMALLINT UNSIGNED NOT NULL; Query OK, 9 rows affected (0.05 sec) Records: 9 Duplicates: 0 Warnings: 0 mysql> SELECT*FROM sword; +----+--------+-------+------+-------+---------+---------+ | id | name | atk | hit | crit | attr_id | type_id | +----+--------+-------+------+-------+---------+---------+ | 1 | 黑風 | 10800 | 400 | 400 | 2 | 3 | | 2 | 木藜 | 5400 | 200 | 200 | 2 | 1 | | 3 | 荊戈 | 8020 | 1000 | 10 | 5 | 6 | | 4 | 痕兮 | 8998 | 800 | 999 | 3 | 4 | | 5 | 逐暮 | 100 | 1000 | 10000 | 4 | 5 | | 6 | 風躍 | 9020 | 10 | 10 | 2 | 2 | | 8 | 洛神 | 20020 | 1 | 10 | 5 | 3 | | 9 | 隱鋒 | 8020 | 2000 | 10 | 1 | 1 | +----+--------+-------+------+-------+---------+---------+ 9 rows in set (0.01 sec) mysql> DESC sword; +---------+----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------+----------------------+------+-----+---------+----------------+ | id | smallint(5) unsigned | NO | PRI | NULL | auto_increment | | name | varchar(32) | NO | | NULL | | | atk | smallint(5) unsigned | NO | | NULL | | | hit | smallint(5) unsigned | NO | | NULL | | | crit | smallint(5) unsigned | YES | | 10 | | | attr_id | smallint(5) unsigned | NO | | NULL | | | type_id | smallint(5) unsigned | NO | | NULL | | +---------+----------------------+------+-----+---------+----------------+ 7 rows in set (0.00 sec)
這樣表中兩列重複漢字都用數字等價替換，減小表的體積。class
錶鏈接
添加兩條類型
mysql> INSERT sword_type(type_name) VALUES('獸界'),('佛界'); Query OK, 2 rows affected (0.42 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> SELECT*FROM sword_type; +---------+-----------+ | type_id | type_name | +---------+-----------+ | 1 | 人界 | | 2 | 仙界 | | 3 | 神界 | | 4 | 道界 | | 5 | 鬼界 | | 6 | 魔界 | | 7 | 獸界 | | 8 | 佛界 | +---------+-----------+ 8 rows in set (0.00 sec)
添加兩條屬性sso
mysql> INSERT sword_attr(attr) VALUES('光'),('暗'); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> SELECT*FROM sword_attr; +---------+------+ | attr_id | attr | +---------+------+ | 1 | 土 | | 2 | 木 | | 3 | 水 | | 4 | 火 | | 5 | 金 | | 6 | 光 | | 7 | 暗 | +---------+------+ 7 rows in set (0.01 sec)
插入一條數據:弒神(attr_id越界)
mysql> INSERT sword VALUES(NULL,'弒神',12000,100,100,10,6); Query OK, 1 row affected (0.00 sec) mysql> SELECT*FROM sword; +----+--------+-------+------+-------+---------+---------+ | id | name | atk | hit | crit | attr_id | type_id | +----+--------+-------+------+-------+---------+---------+ | 1 | 黑風 | 10800 | 400 | 400 | 2 | 3 | | 2 | 木藜 | 5400 | 200 | 200 | 2 | 1 | | 3 | 荊戈 | 8020 | 1000 | 10 | 5 | 6 | | 4 | 痕兮 | 8998 | 800 | 999 | 3 | 4 | | 5 | 逐暮 | 100 | 1000 | 10000 | 4 | 5 | | 6 | 風躍 | 9020 | 10 | 10 | 2 | 2 | | 8 | 洛神 | 20020 | 1 | 10 | 5 | 3 | | 9 | 隱鋒 | 8020 | 2000 | 10 | 1 | 1 | | 10 | 弒神 | 12000 | 100 | 100 | 10| 6 | +----+--------+-------+------+-------+---------+---------+ 10 rows in set (0.00 sec)
INNER JOIN
查詢全部劍的詳細信息(經過內鏈接實現:只呈現正確鏈接的記錄)
因爲弒神的attr_id越界，鏈接不正確，故沒法查出
mysql> SELECT id,name,atk,hit,type_name,attr FROM sword AS s -> INNER JOIN sword_type AS t ON s.type_id = t.type_id -> INNER JOIN sword_attr AS a ON s.attr_id = a.attr_id; +----+--------+-------+------+-----------+------+ | id | name | atk | hit | type_name | attr | +----+--------+-------+------+-----------+------+ | 1 | 黑風 | 10800 | 400 | 神界 | 木 | | 2 | 木藜 | 5400 | 200 | 人界 | 木 | | 3 | 荊戈 | 8020 | 1000 | 魔界 | 金 | | 4 | 痕兮 | 8998 | 800 | 道界 | 水 | | 5 | 逐暮 | 100 | 1000 | 鬼界 | 火 | | 6 | 風躍 | 9020 | 10 | 仙界 | 木 | | 8 | 洛神 | 20020 | 1 | 神界 | 金 | | 9 | 隱鋒 | 8020 | 2000 | 人界 | 土 | +----+--------+-------+------+-----------+------+ 8 rows in set (0.00 sec)
LEFT JOIN
查詢全部劍的詳細信息(左外鏈接：左表所有，右表無匹配則置空)
mysql> SELECT id,name,atk,hit,type_name,attr FROM sword AS s -> LEFT JOIN sword_type AS t ON s.type_id = t.type_id -> LEFT JOIN sword_attr AS a ON s.attr_id = a.attr_id; +----+--------+-------+------+-----------+------+ | id | name | atk | hit | type_name | attr | +----+--------+-------+------+-----------+------+ | 1 | 黑風 | 10800 | 400 | 神界 | 木 | | 2 | 木藜 | 5400 | 200 | 人界 | 木 | | 3 | 荊戈 | 8020 | 1000 | 魔界 | 金 | | 4 | 痕兮 | 8998 | 800 | 道界 | 水 | | 5 | 逐暮 | 100 | 1000 | 鬼界 | 火 | | 6 | 風躍 | 9020 | 10 | 仙界 | 木 | | 8 | 洛神 | 20020 | 1 | 神界 | 金 | | 9 | 隱鋒 | 8020 | 2000 | 人界 | 土 | | 10 | 弒神 | 12000 | 100 | 魔界 | NULL | +----+--------+-------+------+-----------+------+ 9 rows in set (0.00 sec)
RIGHT JOIN
查詢全部劍的詳細信息(左外鏈接：右表所有，左表無匹配則置空)
mysql> SELECT id,name,atk,hit,type_name,attr FROM sword AS s -> RIGHT JOIN sword_type AS t ON s.type_id = t.type_id -> RIGHT JOIN sword_attr AS a ON s.attr_id = a.attr_id; +------+--------+-------+------+-----------+------+ | id | name | atk | hit | type_name | attr | +------+--------+-------+------+-----------+------+ | 9 | 隱鋒 | 8020 | 2000 | 人界 | 土 | | 1 | 黑風 | 10800 | 400 | 神界 | 木 | | 2 | 木藜 | 5400 | 200 | 人界 | 木 | | 6 | 風躍 | 9020 | 10 | 仙界 | 木 | | 4 | 痕兮 | 8998 | 800 | 道界 | 水 | | 5 | 逐暮 | 100 | 1000 | 鬼界 | 火 | | 3 | 荊戈 | 8020 | 1000 | 魔界 | 金 | | 8 | 洛神 | 20020 | 1 | 神界 | 金 | | NULL | NULL | NULL | NULL | NULL | 光 | | NULL | NULL | NULL | NULL | NULL | 暗 | +------+--------+-------+------+-----------+------+ 10 rows in set (0.00 sec)