问一道SQL查询语句

Question

问一道SQL查询语句

有一张表：t_student
字段：
id
name
age
status (0,1,2,3,4,5,6)
teacher_id

问：如果teacher_id是空，就不查询status=0
这种SQL语句怎么写？

Answer 1

select * from test.t_student where (teacher_id ='' and status != '0') or teacher_id != '';

Answer 2

select * from t_student where teacher_id='' and status!=0

Answer 3

WITH T AS (
  SELECT 1 AS ID, 'A' AS NAME, 21 AS AGE, 0 AS STATUS, 1 AS TEACHERID FROM DUAL UNION ALL 
  SELECT 2 AS ID, 'B' AS NAME, 20 AS AGE, 1 AS STATUS, 1 AS TEACHERID FROM DUAL UNION ALL
  SELECT 3 AS ID, 'C' AS NAME, 21 AS AGE, 2 AS STATUS, 2 AS TEACHERID FROM DUAL UNION ALL
  SELECT 4 AS ID, 'D' AS NAME, 22 AS AGE, 3 AS STATUS, 3 AS TEACHERID FROM DUAL UNION ALL
  SELECT 5 AS ID, 'E' AS NAME, 23 AS AGE, 0 AS STATUS, NULL AS TEACHERID FROM DUAL 
)
SELECT * FROM T
WHERE (TEACHERID IS NULL AND STATUS <> 0) OR TEACHERID IS NOT NULL;