update table with 4 columns specified, but only 2 columns are available

问题

I have one table called test, which has 4 columns:

id     INT
v_out  INT
v_in   INT
label  CHARACTER

I'm trying to update the table with the following query:

String sql = "
    update
        test
    set
        v_out = temp.outV
        , v_in = temp.inV
        , label = temp.label
    from (
            values(
                (1,234,235,'abc')
                ,(2,234,5585,'def')
            )
        ) as temp (e_id, outV, inV, label)
    where
        id = temp.e_id
";

When I execute it, I got the error:

org.postgresql.util.PSQLException: ERROR:

 table "temp" has 2 columns available but 4 columns specified

Whats the problem, and how can i solve it?

回答1:

The values for the values clause must not be enclosed in parentheses:

values (
    (1,234,235,'abc'), (2,234,5585,'def')
) 

creates a single row with two columns. Each column being an anonymous "record" with 4 fields.

What you want is:

from (
        values 
            (1,234,235,'abc'), 
            (2,234,5585,'def')
    ) as temp (e_id, outV, inV, label)

SQLFiddle showing the difference: http://sqlfiddle.com/#!15/d41d8/2763

This behavior is documented, but that is quite hard to find:
http://www.postgresql.org/docs/current/static/rowtypes.html#AEN7362

It's essentially the same thing as select (col1, col2) from some_table vs. select col1, col2 from some_table. The first one returns one column with an anonymous composite type that has two fields. The second one returns two columns from the table.

来源：https://stackoverflow.com/questions/25059350/update-table-with-4-columns-specified-but-only-2-columns-are-available