二进制字符串函数和操作符
字符串操作符
SQL定义了一些字符串函数,在这些函数里使用关键字而不是逗号来分隔参数。
- octet_length(string)
返回值类型:int
示例:
1 2 3 4 5
openGauss=# SELECT octet_length(E'jo\\000se'::bytea) AS RESULT; result -------- 5 (1 row)
- overlay(string placing string from int [for int])
返回值类型:bytea
示例:
1 2 3 4 5
openGauss=# SELECT overlay(E'Th\\000omas'::bytea placing E'\\002\\003'::bytea from 2 for 3) AS RESULT; result ---------------- \x5402036d6173 (1 row)
- position(substring in string)
返回值类型:int
示例:
1 2 3 4 5
openGauss=# SELECT position(E'\\000om'::bytea in E'Th\\000omas'::bytea) AS RESULT; result -------- 3 (1 row)
- substring(string [from int] [for int])
返回值类型:bytea
示例:
1 2 3 4 5
openGauss=# SELECT substring(E'Th\\000omas'::bytea from 2 for 3) AS RESULT; result ---------- \x68006f (1 row)
- substr(bytea [from int] [for int])
返回值类型:bytea
示例:
1 2 3 4 5
openGauss=# select substr(E'Th\\000omas'::bytea,2, 3) as result; result ---------- \x68006f (1 row)
- trim([both] bytes from string)
描述:从string的开头和结尾删除只包含bytes中字节的最长字符串。
返回值类型:bytea
示例:
1 2 3 4 5
openGauss=# SELECT trim(E'\\000'::bytea from E'\\000Tom\\000'::bytea) AS RESULT; result ---------- \x546f6d (1 row)
二进制字符串函数
GaussDB也提供了函数调用所使用的常用语法。
- btrim(string bytea,bytes bytea)
描述:从string的开头和结尾删除只包含bytes中字节的最长的字符串。
返回值类型:bytea
示例:
1 2 3 4 5
openGauss=# SELECT btrim(E'\\000trim\\000'::bytea, E'\\000'::bytea) AS RESULT; result ------------ \x7472696d (1 row)
- get_bit(string, offset)
返回值类型:int
示例:
1 2 3 4 5
openGauss=# SELECT get_bit(E'Th\\000omas'::bytea, 45) AS RESULT; result -------- 1 (1 row)
- get_byte(string, offset)
返回值类型:int
示例:
1 2 3 4 5
openGauss=# SELECT get_byte(E'Th\\000omas'::bytea, 4) AS RESULT; result -------- 109 (1 row)
- set_bit(string,offset, newvalue)
返回值类型:bytea
示例:
1 2 3 4 5
openGauss=# SELECT set_bit(E'Th\\000omas'::bytea, 45, 0) AS RESULT; result ------------------ \x5468006f6d4173 (1 row)
- set_byte(string,offset, newvalue)
返回值类型:bytea
示例:
1 2 3 4 5
openGauss=# SELECT set_byte(E'Th\\000omas'::bytea, 4, 64) AS RESULT; result ------------------ \x5468006f406173 (1 row)
- rawcmp
参数:raw, raw
返回值类型:integer
- raweq
参数:raw, raw
返回值类型:boolean
- rawge
参数:raw, raw
返回值类型:boolean
- rawgt
参数:raw, raw
返回值类型:boolean
- rawin
参数:cstring
返回值类型:bytea
- rawle
参数:raw, raw
返回值类型:boolean
- rawlike
参数:raw, raw
返回值类型:boolean
- rawlt
参数:raw, raw
返回值类型:boolean
- rawne
参数:raw, raw
返回值类型:boolean
- rawnlike
参数:raw, raw
返回值类型:boolean
- rawout
参数:bytea
返回值类型:cstring
- rawsend
参数:raw
返回值类型:bytea
- rawtohex
参数:text
返回值类型:text