没有为“ src”合并语句SQL服务器的列1指定列名

Question

I am using the MERGE statement in SQL server to refresh the data but I am repeatedly getting this error int the ON clause of the MERGE statement. The code is

    DECLARE @instance varchar(50)
    DECLARE @db varchar (50)
    DECLARE @queryEntity nvarchar(max)

    SET @instance = (select value from Parameter where name = 'SERVERALIAS')
    SET @db = (select value from Parameter where name = 'SERVERDB')

    SET @queryEntity = 'Select EntityId,EntityName,CreatedDate,ModifiedDate,Active,TENANTID,PriorityId From [' + @instance + '].[' + @db + '].metadata.Entity Where TENANTID = 1'

    MERGE [metadata].[Entity] AS trgt
    USING ( VALUES(@queryEntity) ) AS src

    ON ( **trgt.EntityId = src.EntityId** ) 

    WHEN matched 
    --AND trgt.ModifiedDate <= src.ModifiedDate 
    THEN 
      -- if the master has a row newer than the client
      -- update the client                      
      UPDATE SET trgt.EntityId = src.EntityId, 
                 trgt.EntityName = src.EntityName, 
                 trgt.Createddate = src.CreatedDate, 
                 trgt.ModifiedDate = src.ModifiedDate, 
                 trgt.Active = src.Active, 
                 trgt.TENANTID = src.TENANTID, 
                 trgt.PriorityId = src.PriorityId      

    WHEN NOT matched BY SOURCE
    THEN 
      DELETE 

    WHEN NOT matched BY TARGET
    THEN 
      INSERT ( EntityId, EntityName, CreatedDate, ModifiedDate, Active, TENANTID, PriorityId) 
      VALUES ( src.EntityId, src.EntityName, src.CreatedDate, src.ModifiedDate, src.Active, src.TENANTID, src.PriorityId); 

Answer 1

You haven't specified a column name for src -- the message is pretty clear. Try this:

MERGE [metadata].[Entity] AS trgt
USING ( VALUES(@queryEntity) ) AS src(EntityId)
--------------------------------------^

I should point out that this is only the beginning. src also doesn't have a host of other columns, specified in the rest of the MERGE . In fact, it is merely a string. MERGE doesn't execute a string just because it looks like a query.

You have three options. The first is to dispense with the variable and put the query string in the MERGE . But that doesn't seem possible because you have variable identifier names.

The second is to use dynamic SQL with the MERGE .

My recommendation, though, is to use dynamic SQL to create a view or to populate a table with a canonical name. Then use that for the MERGE statement.