Question

我想对下表使用更新命令。我想要做的是根据answer列更新reference列：第二和第三个答案应为A，因为它们的引用为1，第一行的答案为A，类似于5和6应该是X。

示例数据：

id    answer  ref
-------------------
1       A      1
2       B      1
3       C      1
4       x      4
5       y      4
6       z      4

Answer 1

update a
set a.answer = b.answer
from tablename a, tablename b
where a.ref = b.id

编辑：添加这个也可能更好;

and a.ref <> a.id

Answer 2

update table1 t1 set answer = t2.answer from table1 t2 where t1.ref = t2.id;

Answer 3

您可以使用case声明

UPDATE sample_data
SET answer = ref
WHERE CASE 
      WHEN ref = 1
      THEN answer = 'A' 
      ELSE
      WHEN REF = 4
      THEN ANSWER = 'x'
END as available

SQL Server：更新同一个表中的值

3 个答案: