SQL查询...我需要从表1的同一列中插入2个值到表2的2个不同列中

Question

insert into friends (user_id1,user_id2) select user_id from user where UserName='summer'or UserName='winter' This gives an error. I want to insert user_id of 'summer' into user_id1 and user_id of 'winter' into user_id2. Please help?

Answer 1

insert into friends (user_id1,user_id2) 
select user_id, -1 from user where UserName='summer'

update friends 
set user_id2 = (select user_id from user where UserName='winter')
where user_id2 = -1

Answer 2

Select must have same number of columns as insert, therefore:

INSERT INTO friends (user_id1,user_id2)
SELECT (SELECT user_id FROM user where UserName='Summer') AS user_id1, (SELECT user_id FROM user WHERE UserName='Winter') AS user_id2

Should do the trick

Answer 3

INSERT INTO table2 (user_id1,user_id2)
SELECT
  (SELECT UserName
   FROM table1
   WHERE UserName='Summer') AS user_id1,

  (SELECT UserName
   FROM table1
   WHERE UserName='Winter') AS user_id2

SQL FIDDLE