SELECT (array_agg(id ORDER BY total DESC))[1] AS id , customer_id , max(total) AS total FROM purchases GROUP BY customer_id; 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 但是这里出现了customer_id的 自动升序,看了些帖子。 Results(性能) Execution time for above queries withEXPLAIN ANALYZE...
SELECTid,customer_id,total ,row_number()OVER(PARTITIONBYcustomer_idORDERBYtotalDESC)ASrn FROMpurchases ) SELECTid,customer_id,total FROMcte WHERErn=1; 2.row_number()in subquery (my optimization) 子查询 SELECTid,customer_id,total FROM( SELECTid,customer_id,total ,row_number()OVER(PARTITIONBY...
在SQL中,GROUP BY子句用于将结果集按一列或多列进行分组,而HAVING子句则用于在分组的基础上对分组进行过滤。这两者通常一起使用,允许在执行聚合函数后对分组应用条件。 GROUP BY 子句 GROUP BY子句的基本语法如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECT column1, column2, ..., aggregate_...
SQL 中Group By语句大家都很熟悉,根据指定的规则对数据进行分组,常常和聚合函数一起使用。 比如,考虑有表dealer,表中数据如下: 如果执行 SQL 语句SELECT id, sum(quantity) FROM dealer GROUP BY id ORDER BY id,会得到如下结果: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 +---+---+|id|sum(qu...
Select Multiple Columns To select more than one column, just separate them with a comma. For instance, SELECT FirstName, LastName FROM Person.Person returns both the first name and last name as a result. In case you wondering you can mix the case when writing queries. That is ...
SELECTemployees.employee_id,employees.first_name,employees.last_name,departments.department_nameFROM...
SQL 中 Group By 语句大家都很熟悉,根据指定的规则对数据进行分组,常常和聚合函数一起使用。 比如,考虑有表 dealer,表中数据如下: 如果执行 SQL 语句 SELECT id, sum(quantity) FROM dealer GROUP BY id ORDER BY id,会得到如下结果: +---+---+ | id|sum(quantity...
SQL 中Group By语句大家都很熟悉,根据指定的规则对数据进行分组,常常和聚合函数一起使用。 比如,考虑有表dealer,表中数据如下: 如果执行 SQL 语句SELECT id, sum(quantity) FROM dealer GROUP BY id ORDER BY id,会得到如下结果: +---+---+ | id|sum(quantity...
How to select the first/least/max row per group in SQL Here are some common SQL problems, all of which have related solutions: how do I find the most recent log entry for each program? How do I find the most popular item from each category? How do I find the top score for each ...
ROW, ROWS, ROW_COUNT, ROW_NUMBER, SAVEPOINT, SCALE, SCHEMA, SCHEMA_NAME, SCOPE, SCOPE_CATALOGS, SCOPE_NAME, SCOPE_SCHEMA, SCROLL, SEARCH, SECOND, SECTION, SECURITY, SELECT, SELF, SENSITIVE, SEQUENCE, SERIALIZABLE, SERVER, SERVER_NAME, SESSION, SESSION_USER, SET, SETS, SIMILAR, SIMPLE, SIZ...