当 ID 匹配时，我需要将第二个表中的值插入到第一个表中

Question

I have 2 tables. Below is the fields description. 1st table Fields: EmployeeID, Name, EmployeeStatus, PreferredName

2nd table Fields: EmployeeID, PreferredName

I need to insert the values of PreferredName from 2nd table to the first table whenever EmployeeID matches. Currently all values of PreferredName in the 1st table are null. If no match by EmployeeID they should remain null. This is SQL Server.

I am trying something like:

insert into  [Table1] PreferredName  values 

SELECT  
      [PreferredName]

  FROM [Table2]
  where [EmployeeID] in (SELECT  EmployeeID FROM [Table1]

Answer 1

I think you actually want to UPDATE the table, not INSERT new data. For that, you can use an UPDATE with JOIN query:

UPDATE table1
SET table1.PreferredName = table2.PreferredName
FROM table1
JOIN table2 ON table2.EmployeeID = table1.EmployeeID

Demo on dbfiddle

Answer 2

you can use not exists keyword

insert into table1 (preferredname) 
select t2.preferredname
from table2 t1 where
    not exists (select 1 from table1 t1 where t1.preferredname = t2.preferredname)