PostgreSQL 字符串处理与日期处理操作_PostgreSQL_

 SELECT CHAR_LENGTH('test') -- 字符串长度 SELECT LENGTH('test') LENGTH(string,encoding name) SELECT LENGTH('测试','UTF-8'); LOWER(string) 或者 UPPER(string) -- 大小写 ASCII(string) SELECT ASCII('abc') -- 结果是'a'的ascii码

 FORMAT(formatstr text [,formatarg "any" [, ...] ]) -- 类似于printf

 SELECT 'number' || 123 --字符串连接 CONCAT(str "any" [, str "any" [, ...] ]) CONCAT_WS(sep text, str "any" [,str "any" [, ...] ]) SELECT * FROM CONCAT_WS('#','hello','world')

 LPAD(string text, length int [,fill text]) RPAD(string text, length int [,fill text]) SELECT LPAD('12345', 10,'0') -- 结果 "0000012345" TRIM([leading | trailing | both] [characters] from string) SELECT TRIM(both ' ' from ' hello world') -- 结果是'hello world' BTRIM(string text [, characters text]) RTRIM(string text [, characterstext]) LTRIM(string text [, characterstext]) SELECT BTRIM('yyhello worldyyyy','y') -- 结果是'hello world' LEFT(str text, n int) -- 返回字符串前n个字符，n为负数时返回除最后|n|个字符以外的所有字符 RIGHT(str text, n int) SUBSTRING(string from int [for int]) SELECT SUBSTRING('hello world' from 7 for 5) -- 结果是'world'

 QUOTE_IDENT(string text) QUOTE_LITERAL(STRING TEXT) QUOTE_LITERAL(value anyelement) SELECT 'l''host"' -- 结果是'l'host"' SELECT QUOTE_LITERAL('l''host"') -- 结果是'l''host"'

 SPLIT_PART(string text,delimiter text, field int) REGEXP_SPLIT_TO_ARRAY(stringtext, pattern text [, flags text]) REGEXP_SPLIT_TO_TABLE(stringtext, pattern text [, flagstext]) SELECT SPLIT_PART('hello#world','#',2) -- 结果是'world' SELECT REGEXP_SPLIT_TO_ARRAY('hello#world','#') -- 结果是{hello,world} SELECT REGEXP_SPLIT_TO_TABLE('hello#world','#') as split_res -- 结果是两行,第一行hello,第二行world

 POSITION(substring in string) -- 查找 SELECT POSITION('h' in 'hello world') -- 结果是1，这里从1开始计数 REVERSE(str) REPEAT(string text, number int) REPLACE(string,string,string) SELECT REPLACE('hello world',' ','#') REGEXP_MATCHES(string text,pattern text [, flags text]) REGEXP_REPLACE(string text,pattern text,replacement text[, flags text]) SELECT REGEXP_MATCHES('hello world','.o.','g') -- 返回两行，第一行是'lo ',第二行是'wor' SELECT REGEXP_MATCHES('hello world','.o.') -- 返回第一个匹配，'lo '

 SELECT TO_CHAR(TO_TIMESTAMP(CREATE_TIME),'YYYY-MM-DD HH24:MI:SS') SELECT EXTRACT(YEAR FROM NOW());

 AND to_timestamp(a.upload_time,'yyyy-MM-dd')>='"+startTime+"' and to_timestamp(a.upload_time,'yyyy-MM-dd') <= '"+endTime+"' 

 substring('2019-04-08 14:18:09',index,k):

 SELECT substring(upload_time,1,10) from table WHERE upload_time='2019-04-08 14:18:09'

 SELECT substring(upload_time,12,5) from table WHERE upload_time='2019-04-08 14:18:09'