size() != 2) throw new RuntimeException("currently supports only 2 tables join"); JoinSelect joinSelect = createBasicJoinSelectAccordingToTableSource((SQLJoinTableSource) query.getFrom()); List<Hint> hints = parseHints(query.getHints()); joinSelect.setHints(hints); String firstTableAlias =...
select FirstName, LastName, City, Statefrom Person left join Addresson Person.PersonId = Address.PersonId 注意: 1) 两个列表没有同样列名,select可以直接输入列名,不用指定表名 2)用left join不用right join, inner join 或者full join,对应满足person表里的内容 3) on 之后填写两个表中同时存在的列名...
In the previous tutorial, you learned how to query data from a single table using theSELECT statement. However, you often want to query data from multiple tables to have a complete result set for analysis. To query data from multiple tables you use join statements. SQL provides several types...
SELECTStudents.ID,Students.Name,Majors.NameASMajorNameFROMStudentsLEFTJOINMajorsONStudents.MajorID=Majors.ID 结果: 结论: 通过结果,我们可以看到左连接包含了第一张表的所有信息,在第二张表中如果没有匹配项,则用NULL代替。 2)RIGHT JOIN(right outer join)右外连接(右连接) 右外连接保留了第二个表的所有行...
show tables; select * from location; select * from store_info; --- SELECT ---显示表格中一个或数个字段的所有数据记录 语法:SELECT "字段" FROM "表名"; SELECT Store_Name FROM Store_Info; select可以指定字段顺序去显示字段 select Date,Store_Name,Sales from store_info; select Date,Sales...
select student.Id,Name,wife.wife_name from student right join wife on student.Id=wife.id order by student.Id 按照sql标准CROSS JOIN是笛卡尔积。但对于mysql来说,CROSS JOIN 相当于 INNER JOIN和JOIN。 如果想把空值用其他文字数值替代: select student.Id,ifnull(Name,'没有'),ifnull(wife.wife_name...
了解使用各种 JOIN 运算访问来自多个表的数据的 T-SQL 查询。 学习目标 完成本模块后,你将能够: 描述联接概念和语法 编写使用内部联接和外部联接的查询 编写使用交叉联接的查询 编写使用自联接的查询 开始 添加 添加到集合 添加到计划 添加到挑战 先决条件 ...
It selects specific columns from these tables: 'bill_no' and 'bill_amt' from the 'counter_sale' table, and 'item_name' from the 'foods' table. The query uses a LEFT JOIN to combine rows from the 'counter_sale' table with matching rows from the 'foods' table. ...
SELECT QUOTENAME(s.[name])+'.'+QUOTENAME(t.[name]) as Table_name , i.[name] as Index_name , p.partition_number as Partition_nmbr , p.[rows] as Row_count , p.[data_compression_desc] as Data_Compression_desc FROM sys.partitions p JOIN sys.tables t ON p.[object_id] =...
matches rows using all shared columns, or keys, in both database tables. The outer join retains the matched and unmatched rows between the two tables. Executing this function is the equivalent of writing the SQL statementSELECT * FROM lefttable,righttable OUTER JOIN lefttable.key = righttable...