常用SQL

空值转为 0

• MySQL

case when (col > ) then col else 0 end

固定长度数字

• MySQL

substr(concat('00000', floor(rand() * 1000000)), -6)

近一百天内时间

• Doris

date_add(now(), - rand() * 100)

• MySQL

date_add(now(), interval - RAND() * 100 day)

生成连续数字

• MySQL

with recursive seq(no) as(
    select   1  no
    union all
    select   no+1  no
    from     seq
    where    no < 100
)
select   no
from     seq

• MySQL, Doris, Oracle

with t1 as (
   with a as (
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL 
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
   ),
   b as (
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL 
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
   )
   select 1 from a, b
),
t2 as (
   with a as (
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL 
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
   ),
   b as (
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL 
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
   )
   select 1 from a, b
),
t3 as (
   with a as (
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL 
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
   ),
   b as (
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL 
      SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
   )
   select 1 from a, b
   limit 100
)
select 1 from t1, t2, t3