一、sql指定排序規則
1. oracle
select l.*
from learner l
where l.study_num in ('1760010025', '1660030817', '1860039508', '1660056123')
order by instr('1760010025,1660030817,1860039508,1660056123', l.study_num)
需要注意的是instr(參數1,參數2)方法,“參數1”爲一個單號內逗號分隔的字符串;“參數2”爲指定排序的字段。
2. mysql
select l.*
from learner l
where l.study_num in ('1760010025', '1660030817', '1860039508', '1660056123')
order by FIELD(l.study_num, '1760010025', '1660030817', '1860039508', '1660056123')
二、 篩選id最大記錄
當兩條數據重複需要刪除id最大或最小的一條記錄時候,前提是id爲自增長的數字
SELECT
i.*
FROM
t_bas_learner l,
t_fee_invoice i
WHERE
l.LEARNER_ID = i.LEARNER_ID
AND i.INVOICE_ID = (
SELECT
max(i2.INVOICE_ID)
FROM
t_fee_invoice i2
WHERE
l.LEARNER_ID = i2.LEARNER_ID
)
AND l.STUDY_NUM IN (
'18114120042',
'18114120001'
)
這裏記錄的是批量刪除id最大記錄。如果id最小max替換爲min
三、查詢插入數據
mysql 相對簡單,一般mysql中的id都爲自動生成,不用關心。
insert into table2(testname,createtime,falg)
select t1.testname,t1.createtime,t1.falg from table1 t1;
oracle表中自增長的id是維護在sequences中,名稱規則一般爲SEQ_表名
insert into table2(id,testname,createtime,falg)
select seq_table2.nextval, t1.testname,t1.createtime,t1.falg from table1 t1;
seq_table2.nextval 爲查詢table2表的自增長id