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姣忔櫄涔濈偣: 鎶€鏈共璐?馃憠 蹇呭畾濂変笂
鍝堝柦锛屽悇浣嶆柊鏉ョ殑灏忎紮浼翠滑锛屽ぇ瀹跺ソ锛佺敱浜庡叕浼楀彿鍋氫簡鏀圭増锛屼负浜嗕繚璇佸叕浼楀彿鐨勮祫婧愯兘鍑嗘椂鎺ㄩ€佸埌浣犳墜閲岋紝澶у璁板緱灏嗗挶浠殑鍏紬鍙?nbsp;鍔犳槦鏍囩疆椤?/span> 锛屽湪姝ょ湡璇氱殑琛ㄧず鎰熻阿
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鏁板瓧绫诲瀷
鏁村瀷绫诲瀷
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鍙互鐪嬪埌锛孧ySQL 鎻愮ず鐢ㄦ埛璁＄畻鐨勭粨鏋滆秴鍑轰簡鑼冨洿銆傚叾瀹烇紝杩欓噷 MySQL 瑕佹眰 unsigned 鏁板€肩浉鍑忎箣鍚庝緷鐒朵负 unsigned锛屽惁鍒欏氨浼氭姤閿欍€?/p>
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MySQL 涔嬪墠鐨勭増鏈腑瀛樺湪娴偣绫诲瀷 Float 鍜?Double锛屼絾杩欎簺绫诲瀷鍥犱负涓嶆槸楂樼簿搴︼紝涔熶笉鏄?SQL 鏍囧噯鐨勭被鍨嬶紝鎵€浠ュ湪鐪熷疄鐨勭敓浜х幆澧冧腑涓嶆帹鑽愪娇鐢?/strong>锛屽惁鍒欏湪璁＄畻鏃讹紝鐢变簬绮惧害绫诲瀷闂锛屼細瀵艰嚧鏈€缁堢殑璁＄畻缁撴灉鍑洪敊銆?/p>
鏇撮噸瑕佺殑鏄紝浠?MySQL 8.0.17 鐗堟湰寮€濮嬶紝褰撳垱寤鸿〃鐢ㄥ埌绫诲瀷 Float 鎴?Double 鏃讹紝浼氭姏鍑轰笅闈㈢殑璀﹀憡锛歁ySQL 鎻愰啋鐢ㄦ埛涓嶈鐢ㄤ笂杩版诞鐐圭被鍨嬶紝鐢氳嚦鎻愰啋灏嗗湪涔嬪悗鐗堟湰涓簾寮冩诞鐐圭被鍨嬨€?/p>
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鍏朵腑锛? 鏄簿搴︼紙绮惧害琛ㄧず淇濆瓨鍊肩殑涓昏浣嶆暟锛夛紝2 鏄爣搴︼紙鏍囧害琛ㄧず灏忔暟鐐瑰悗闈繚瀛樼殑浣嶆暟锛夈€傞€氬父鍦ㄨ〃缁撴瀯璁捐涓紝绫诲瀷 DECIMAL 鍙互鐢ㄦ潵琛ㄧず鐢ㄦ埛鐨勫伐璧勩€佽处鎴风殑浣欓绛夌簿纭埌灏忔暟鐐瑰悗 2 浣嶇殑涓氬姟銆?/p>
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mysql> SHOW CREATE TABLE sale\G
*************************** 1. row ***************************
Table: sale
Create Table: CREATE TABLE `sale` (
`sale_date` date NOT NULL,
`sale_count` int unsigned DEFAULT NULL,
PRIMARY KEY (`sale_date`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci
1 row in set (0.00 sec)
mysql> SELECT * FROM sale;
+------------+------------+
| sale_date | sale_count |
+------------+------------+
| 2020-01-01 | 10000 |
| 2020-02-01 | 8000 |
| 2020-03-01 | 12000 |
| 2020-04-01 | 9000 |
| 2020-05-01 | 10000 |
| 2020-06-01 | 18000 |
+------------+------------+
6 rows in set (0.00 sec)SELECT
s1.sale_date, s2.sale_count - s1.sale_count AS diff
FROM
sale s1
LEFT JOIN
sale s2 ON DATE_ADD(s2.sale_date, INTERVAL 1 MONTH) = s1.sale_date
ORDER BY sale_date;ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in '(`test`.`s2`.`sale_count` - `test`.`s1`.`sale_count`)'mysql> SET sql_mode='NO_UNSIGNED_SUBTRACTION';
Query OK, 0 rows affected (0.00 sec)
SELECT
s1.sale_date,
IFNULL(s2.sale_count - s1.sale_count,'') AS diff
FROM
sale s1
LEFT JOIN sale s2
ON DATE_ADD(s2.sale_date, INTERVAL 1 MONTH) = s1.sale_date
ORDER BY sale_date;
+------------+-------+
| sale_date | diff |
+------------+-------+
| 2020-01-01 | |
| 2020-02-01 | 2000 |
| 2020-03-01 | -4000 |
| 2020-04-01 | 3000 |
| 2020-05-01 | -1000 |
| 2020-06-01 | -8000 |
+------------+-------+
6 rows in set (0.00 sec)娴偣绫诲瀷鍜岄珮绮惧害鍨?/span>
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-> a INT AUTO_INCREMENT PRIMARY KEY
-> );
mysql> INSERT INTO t VALUES (2147483647);
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO t VALUES (NULL);
ERROR 1062 (23000): Duplicate entry '2147483647' for key 't.PRIMARY'mysql> SELECT * FROM t;
+---+
| a |
+---+
| 1 |
| 2 |
| 3 |
+---+
3 rows in set (0.01 sec)
mysql> DELETE FROM t WHERE a = 3;
Query OK, 1 row affected (0.02 sec)
mysql> SHOW CREATE TABLE t\G
*************************** 1. row ***************************
Table: t
Create Table: CREATE TABLE `t` (
`a` int NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`a`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci
1 row in set (0.00 secmysql> SHOW CREATE TABLE t\G
*************************** 1. row ***************************
Table: t
Create Table: CREATE TABLE `t` (
`a` int NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`a`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci
1 row in set (0.00 s
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CREATE TABLE User (
userId BIGINT AUTO_INCREMENT,
money DECIMAL(8,2) NOT NULL,
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