数据库常用函数整理

1.字符串拼接函数concat(str1,str2)

str1='abc';
str2='efg';
concat(str1,str2)的结果：'abcefg'

 

2.字符串截取函数substr(str1,start,length),left(str1,length),right(str1,length)

str1='abcdefg'
substr(str1,1,3)='abc'
left(str1,3)='abc'
right(str1,3)='efg'

 

3.sql选择判断

select case when str1 is null then 'abcd' 
                  when str1='123' then 'efgh'
                  else 'who'
           end from tablename;

 

实例：

SELECT CASE WHEN TRANS_REMARK IS NOT NULL THEN LEFT(TRANS_REMARK,6) ELSE NEXTVAL FOR UPPSEQ1,'CORE' AS FUNDCHANNELCODE,TRANS_SEQNO,CONCAT(LEFT(TRANS_DATE,4),RIGHT(TRANS_REMARK,10)),TRANS_STATUS FROM OT_TRANS;