UPDATE b SET (ClientName) = (SELECT name FROM a WHERE b.id = a.id) update set from 语句格式 当where和set都需要关联一个表进行查询时,整个update执行时,就需要对被关联的表进行两次扫描,显然效率比较低。 对于这种情况,Sybase和SQL SERVER的解决办法是使用UPDATE…SET…FROM…WHERE…的语法,实际上就是...
UPDATE table1 alias SET (column_name,column_name )=( SELECT column_name, column_name FROM table2 WHERE table2.column_name=alias.column_name) [WHERE column_name= VALUE] 注:若不加where条件则是更新表中的所有数据, 故执行没有where子句的update要慎重再慎重。 实例: 例1: UPDATE t_order t1 SET...
SQL Server 允许我们将 SELECT 结果应用于 UPDATE 语句。我们可以通过 JOIN 来结合 SELECT 结果和更新。以下是整合的 SQL 代码: UPDATEtarget_tableSETtarget_table.column_name=source.new_valueFROMtarget_tableINNERJOINsource_tableASsourceONtarget_table.id=source.idWHEREsome_condition; 1. 2. 3. 4. 5. 在...
如果你的 SQL Server 版本或场景不允许使用 UPDATE ... FROM 语法，你可以考虑以下替代方法：使用 JOIN：UPDATE e SET e.Salary = (SELECT sa.NewSalary FROM SalaryAdjustments sa WHERE e.EmployeeID = sa.EmployeeID)WHERE EXISTS (SELECT 1 FROM SalaryAdjustments sa WHERE e.EmployeeID = sa.EmployeeID)...
SQL Update From Select The problem with the simple UPDATE statement is that it can only take a single table. Why would we want to include a second table? We may have acolumn in one tablebut thevalues for that are derived or calculated from data in another table. ...
UPDATE Table1 SET Column1 = (SELECT ColumnFromTable2 FROM Table2 WHERE Table1.PrimaryKeyColumn = Table2.PrimaryKeyColumn)WHERE EXISTS (SELECT 1 FROM Table2 WHERE Table1.PrimaryKeyColumn = Table2.PrimaryKeyColumn);在这个例子中，子查询 (SELECT ColumnFromTable2 FROM Table2 WHERE Table1.Primary...
(SELECT v1, v2, v3 FROM table2) 答案是可以的,具体的语法如下: UPDATE table1 alias SET (column_name,column_name ) = ( SELECT (column_name, column_name) FROM table2 WHERE column_name = alias.column_name) WHERE column_name = VALUE ...
table_test_update SET story_name = '小猪的糖果屋' WHERE story_id = 102 ; 查看更新后的数据: SELECT * FROM data_learning.table_test_update; 更新后结果如下: 2.2 更新表中的特定行,两列都修改 将story_id = 102的行,story_id更新为99、故事名称更新为'小蚯蚓': UPDATE data_learning.table_test...
第一步,词法分析,一条SQL语句由多个字符串组成,词法分析将提取关键字(比如SELECT,WHERE)、表名、字段名、查询条件等。 第二步,语法分析,判断输入的SQL是否正确,是否符合MySQL的语法。 需要注意的是:判断查询的字段在表中是否存在,也是在分析器这里进行。
UPDATE C_Route test_to SET test_to.RouteFlg = test_from.NoFlg FROM C_Route test_to JOIN C_Route test_from ON (test_to.RouteFlg = test_from.YesFlg AND test_to.CustomerID = test_from.CustomerID AND test_to.StartClientID = test_from.StartClientID AND test_...