如何更新基于列的，其在T-SQL位数据类型的数据

Question

3列（名字，姓氏，状态）

我想更新姓和名测试表对于任何状态，在单个UPDATE查询中的所有行都是真或假。我怎么写这个？

Answer 1

SQL Server bit data type将true/false值存储为1/0，并将字符串'true'和'false'分别转换为1和0。因此，您可以基于'0'或'1'或'False'或'True'进行查询。

如果您希望逻辑使用单个更新查询更新所有行，并根据[Status]列，那么你需要一个case声明：

有多种方法可以做到这一点，其一些实例可以在实例中可以看出和结果如下：

-- Let's make a test table that mimicks your schema and put some data in it  
-- We will use a function to re-make the table 
Create Function MakeTestTable() 
Returns @Test Table (
    FirstName varchar(50), 
    LastName varchar(50), 
    [Status] bit 
) 
As Begin 
    Insert Into @Test Values 
      ('John', 'Doe', 'false'), 
      ('Jane', 'Dane', 'true'), 
      ('Space', 'Cadet', Null) 
    Return 
End 
Go 

-- Our local test table variable for examples: 
Declare @Test Table (
    FirstName varchar(50), 
    LastName varchar(50), 
    [Status] bit 
) 

-- Let's seed the test table 
Insert Into @Test Select * From MakeTestTable() 

-- Verify initial Values 
Select * From @Test 

-- Single update statement depending on [Status] value using Case statement: 
Update @Test 
Set FirstName = 
    Case -- Here we use 1/0 for True/False, respectively 
     When [Status] = 1 Then 'FirstName updated while Status was True' 
     When [Status] = 0 Then 'FirstName updated while Status was False' 
     Else 'FirstName updated while Status was Null' 
    End, 
    LastName = 
    Case -- Here we use 'True' and 'False' which SQL converts to 1 and 0, respectively 
     When [Status] = 'True' Then 'LastName updated while Status was True' 
     When [Status] = 'False' Then 'LastName updated while Status was False' 
     Else 'LastName updated while Status was Null' 
    End 

-- Verify our updates: 
Select * From @Test 

-- Reset for next example: 
Delete @Test; Insert Into @Test Select * From MakeTestTable() 

-- Single update statement based on [Status] value not being null using Case statement: 
Update @Test 
Set FirstName = 
    Case -- Here we update if the value of [Status] is either 0 or 1 using In clause 
     When [Status] In (0,1) Then 'FirstName updated while Status was True or False' 
     Else 'FirstName updated while Status was neither 0 nor 1' 
    End, 
    LastName = 
    Case -- Here we base our update on [Status] being null (reverse of the above) 
     When [Status] Is Not Null Then 'LastName updated while Status was Not Null' 
     Else 'LastName updated while Status was Null' 
    End 

-- Verify our updates: 
Select * From @Test 

-- Reset for next example: 
Delete @Test; Insert Into @Test Select * From MakeTestTable() 

-- Finally, update all columns based on status not being null using Where clause: 
-- Without the CASE statement, the WHERE clause is applied to the entire update, 
-- The code is simpler, but you lose the ability to update each column based on a 
-- different condition. 
Update @Test 
Set FirstName = 'FirstName updated while Status is not Null', 
    LastName = 'LastName updated while Status is not Null' 
Where [Status] Is Not Null 

-- Verify our updates: 
Select * From @Test 

-- Clean up 
Drop Function MakeTestTable 

Answer 2

如果状态不不允许null，则每行是真还是假

update table set firstname = 'fname'; 

如果情况确实允许null，则

update table set firstname = 'fname' where status is not null; 

，如果你有不同的价值观不同的更新就用两个更新

update table set firstname = 'fnameT' where status = 'true'; 
update table set firstname = 'fnameF' where status = 'false';