postgreSQL与Kingbase 字符串裁剪区别

--postgreSQL

postgres=# select substring('abcdefg',0,4);

substring

abc

(1 行记录)

postgres=# select substring('abcdefg',1,4);

substring

abcd

(1 行记录)

postgres=# select substring('abcdefg',-1,4);

substring

ab

(1 行记录)

--kingbase

TEST=# select substring('abcdefg',0,4);

SUBSTRING

abcd

(1 row)

TEST=# select substring('abcdefg',1,4);

SUBSTRING

abcd

(1 row)

TEST=# select substring('abcdefg',-1,4);

SUBSTRING

g

(1 row)