T-SQL查询以从一个表中选择并插入到另一个表中

Question

Please read the question before marking this as a duplicate.

I am trying to insert a row into a table with 5 columns. I want 3 of those columns to come from another table, which I will read using a select query.

INSERT INTO tbl.Log (
     LogDate,
     Object,
     Count,
     Creator,
     LastUpdate)
SELECT TOP 1 
     GETUTCDATE(),
     Object,
     Count, -- I need to +1 to this
     'John Smith',
     LastUpdate
FROM tbl.Objects
WHERE ObjectID = '123'
ORDER BY LastUpdate DESC

I can see what I am doing wrong here:

• GETUTCDATE() should not go in the SELECT because it is not a column name. Where does it go instead?
• The same is true for 'John Smith' as creator
• The Count column is an int; I need to read the existing number and add one to it before inserting it.

I could do this manually by performing two separate queries and parsing the data from the SELECT into the INSERT query, but I am trying to improve my SQL.

Answer 1

You can select values that are not a part of your table and do arithmetic on columns during insert .

INSERT INTO tbl.Log (
     LogDate,
     Object,
     Count,
     Creator,
     LastUpdate)
SELECT TOP 1 
     GETUTCDATE(),
     Object,
     Count+1
     'John Smith',
     LastUpdate
FROM tbl.Objects
WHERE ObjectID = '123'
ORDER BY LastUpdate DESC

Understand that the idea of doing the insert with two separate queries would result in 2 rows.

Answer 2

There is nothing wrong with selecting values that doesn't exist on the table, every RDBMS accepts it.

Also, what do you mean by count+1 ? The count that is inside the log table? If so:

INSERT INTO tbl.Log (
     LogDate,
     Object,
     Count,
     Creator,
     LastUpdate)
SELECT TOP 1 
     GETUTCDATE(),
     Object,
     (SELECT MAX(Count) FROM tbl.log), 
     'John Smith',
     LastUpdate
FROM tbl.Objects
WHERE ObjectID = '123'
ORDER BY LastUpdate DESC

If you meant the count that on the Objects table, that replace the sub select with count+1 , but that just seems like you could have done it your self.