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1、sql按照指定数组顺序查询数据
2、数据库SQL 某字段按首字母排序

基础语句

1、SELECT：选择数据表中的数据

SELECT column_name1, column_name2 FROM table_name;

2、WHERE：筛选符合条件的数据

SELECT column_name FROM table_name WHERE column_name = 'value';

3、AND：用于连接 WHERE 子句中的多个条件

SELECT column_name FROM table_name WHERE column_name1 = 'value1' AND column_name2 = 'value2';

4、OR：用于连接 WHERE 子句中的多个条件，其中至少一个条件必须成立

SELECT column_name FROM table_name WHERE column_name1 = 'value1' OR column_name2 = 'value2';

5、IN：筛选符合指定值中任意一个的数据

SELECT column_name FROM table_name WHERE column_name IN ('value1', 'value2', 'value3');

6、NOT IN：筛选不符合指定值中任意一个的数据

SELECT column_name FROM table_name WHERE column_name NOT IN ('value1', 'value2', 'value3');

7、LIKE：筛选符合指定模式的数据

SELECT column_name FROM table_name WHERE column_name LIKE 'pattern';SELECT column_name FROM table_name WHERE column_name LIKE '%value%'

8、NOT LIKE：筛选不符合指定模式的数据

SELECT column_name FROM table_name WHERE column_name NOT LIKE 'pattern';SELECT column_name FROM table_name WHERE column_name NOT LIKE '%value%'

9、BETWEEN：筛选在指定范围内的数据

SELECT column_name FROM table_name WHERE column_name BETWEEN 'value1' AND 'value2';

9、NOT BETWEEN：筛选不在指定范围内的数据

SELECT column_name FROM table_name WHERE column_name NOT BETWEEN 'value1' AND 'value2';

10、ORDER BY：按指定列进行排序

SELECT column_name FROM table_name ORDER BY column_name ;//默认升序
SELECT column_name FROM table_name ORDER BY column_name DESC;//降序

11、GROUP BY：按指定列进行分组

SELECT column_name1,column_name2  FROM table_name GROUP BY column_name1;

备注： 从 MySQL 5.7.5 开始，默认 SQL 模式包括 ONLY_FULL_GROUP_BY。 （在 5.7.5 之前，MySQL 不检测函数依赖，并且默认不启用 ONLY_FULL_GROUP_BY。），所以select的内容如果不在group by 中，将会报错，可以参考这里的解决方法

DISTINCT ：基于指定列的唯一值去重

SELECT DISTINCT(column_name1) FROM table_name;

区别：distinct和group by具体区别点击查看

12、HAVING：筛选分组后符合指定条件的数据

SELECT column_name1, SUM(column_name2) FROM table_name GROUP BY column_name1 HAVING SUM(column_name2) > 100;

进阶一下

13、JOIN：连接多个数据表

SELECT table1.column_name1, table2.column_name2 FROM table1 JOIN table2 ON table1.column_name1 = table2.column_name1;

14、LEFT JOIN：连接左侧数据表，并包括右侧数据表中与左侧数据表中没有匹配项的行

SELECT table1.column_name1, table2.column_name2 FROM table1 LEFT JOIN table2 ON table1.column_name1 = table2.column_name1;//右连接
SELECT * FROM table1 RIGHT JOIN table2 ON table1.column_name = table2.column_name;

15、UNION：合并多个查询结果

SELECT column_name FROM table1 UNION SELECT column_name FROM table2;

16、EXISTS：检查子查询结果是否存在

SELECT column_name FROM table1 WHERE EXISTS (SELECT column_name FROM table2 WHERE column_name = 'value');//NOT EXISTS：检查子查询结果是否不存在
SELECT column_name FROM table1 WHERE NOT EXISTS (SELECT column_name FROM table2 WHERE column_name = 'value');

17、AVG：计算平均值

SELECT AVG(column_name) FROM table_name;

18、COUNT：计算数据行数

SELECT COUNT(*) FROM table_name;

19、MAX：计算最大值

SELECT MAX(column_name) FROM table_name;

20、MIN：计算最小值

SELECT MIN(column_name) FROM table_name;

21、SUM：计算总和

SELECT SUM(column_name) FROM table_name;

22、CASE：根据条件返回不同的结果

SELECT column_name, CASE WHEN column_name = 'value1' THEN 'result1' WHEN column_name = 'value2' THEN 'result2' ELSE 'result3' END AS new_column_name 
FROM table_name;`

23、ROW_NUMBER：按照指定列进行分组并排序(就是对column_name字段进行分组，并在组内对column_name2字段降序排)

SELECT column_name, ROW_NUMBER() OVER (PARTITION BY column_name ORDER BY column_name2 DESC) FROM table_name;

示例如下：

24、DENSE_RANK：按照指定列进行分组并排序，相同值的行具有相同的排名，不跳过下一个排名（RANK：跳过下一个排名）

SELECT column_name, DENSE_RANK() OVER (PARTITION BY column_name ORDER BY column_name2 DESC) FROM table_name;

示例如下：

25、FIRST_VALUE：返回分组中第一个行的列值

SELECT column_name, FIRST_VALUE(column_name2) OVER (PARTITION BY column_name ORDER BY column_name2) FROM table_name;//返回分组中最后一个行的列值
SELECT column_name, LAST_VALUE(column_name2) OVER (PARTITION BY column_name ORDER BY column_name2 ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FROM table_name;

26、CONCAT：连接多个字符串值为一个字符串

SELECT CONCAT(column_name1, ' ', column_name2) FROM table_name;

示例如下：

附加使用的sql

1、连表更新，将一张表的某个字段更新为另一张表的某个字段值

#将1表的reward更新为b表的reward值
UPDATE project_submits a
INNER JOIN projects b ON a.project_id = b.id 
SET a.reward = b.reward

2、DATE_FORMAT：查询指定日期的数据

	select * from `order_exam_logs` where DATE_FORMAT(created_at, "%Y-%m-%d")='2023-06-05'

因为数据表中created_at存到了秒，所以要使用DATE_FORMAT函数