向 SQL 查询的结果集添加行号

Question

I have a simple select statement. I want to add a temporary column which will number the rows in my result set. I tried this -

declare @num int
set @num = 0;
select t.A, t.B, t.C, (@count + 1) as number
from tableZ as t

It assigns the 1 to all rows. I tried @count = @count + 1 and it did not work. How do I do this thing in a simple manner ?

thanks.

Answer 1

SELECT
    t.A,
    t.B,
    t.C,
    ROW_NUMBER() OVER (ORDER BY (SELECT 1)) AS number
FROM tableZ AS t

See working example at SQLFiddle

Of course, you may want to define the row-numbering order – if so, just swap OVER (ORDER BY (SELECT 1)) for, eg, OVER (ORDER BY tC) , like in a normal ORDER BY clause.

Answer 2

The typical pattern would be as follows, but you need to actually define how the ordering should be applied (since a table is, by definition, an unordered bag of rows):

SELECT t.A, t.B, t.C, number = ROW_NUMBER() OVER (ORDER BY t.A)
  FROM dbo.tableZ AS t
  ORDER BY t.A;

Not sure what the variables in your question are supposed to represent (they don't match).

Answer 3

So before MySQL 8.0 there is no ROW_NUMBER() function. Accpted answer rewritten to support older versions of MySQL:

SET @row_number = 0;
SELECT t.A, t.B, t.C, (@row_number:=@row_number + 1) AS number
FROM dbo.tableZ AS t ORDER BY t.A;