校招求职数据分析岗学SQL、产品运营学SQL的正确姿势是：跟着思扣网SQLintern往死里练。 👉入门教程

这几个不同的目的学SQL，区别还挺大，什么事物锁、触发器、并发锁定、死锁，数分你学他有个卵用，看不懂就跳过没关系的。

笑死，都是学SQL，还有什么区别么，直接看视频干不就完了

校招求职数据分析岗学SQL、产品运营学SQL的正确姿势是，第一步先下载安装数据库软件、自己插入数据、然后对着视频挨个练习；装不上软件就死磕，求爷爷告奶奶一定要把数据库软件装上。

HeLLoWorLd

HeLLoWorLd

HeLLoWorld

HeLLoWorLD

CASE WHEN必须以END结尾

CASE WHEN中必须包含ELSE来处理其他情况

HAVING子句中可以使用别名作为条件

HAVING子句可用于筛选分组后的数据，即使没有使用聚合函数也可以使用它

SELECT * FROM table1 LEFT JOIN table2 ON table1.id=table2.id WHERE table2.status=1;

SELECT * FROM table1 LEFT JOIN table2 ON table1.id=table2.id AND table2.status=1 WHERE table2.id IS NOT NULL;

SELECT * FROM table1 LEFT JOIN table2 ON table1.id=table2.id WHERE table2.status=1 OR table2.id IS NULL;

SELECT * FROM table1 LEFT JOIN table2 ON table1.id=table2.id AND table2.status=1;

DENSE_RANK() OVER (PARTITION BY MONTH(sale_date) ORDER BY sale_amount DESC)

ROW_NUMBER() OVER (PARTITION BY employee_id, MONTH(sale_date) ORDER BY sale_amount DESC)

DENSE_RANK() OVER (PARTITION BY employee_id, MONTH(sale_date) ORDER BY sale_amount DESC)

RANK() OVER (PARTITION BY employee_id, MONTH(sale_date) ORDER BY sale_amount DESC)

FROM → ON → JOIN → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT

SELECT → FROM → WHERE → GROUP BY → HAVING → ORDER BY → LIMIT

FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT

FROM → WHERE → SELECT → GROUP BY → HAVING → ORDER BY → LIMIT