postgresql字符串函数.docx

postgresql字符串函数【Postgresql】字符串操作函数函数：string || string　说明：String concatenation 字符串连接操作例子：Post || greSQL　＝　PostgreSQL函数：string || non-string or non-string || string说明：String concatenation with one non-string input 字符串与非字符串类型进行连接操作例子：Value: || 42 = Value: 42函数：bit_length(string)说明：Number of bits in string 计算字符串的位数例子：bit_length(jose) = 32函数：char_length(string) or character_length(string)说明：Number of characters in string 计算字符串中字符个数例子：char_length(jose) = 4函数：lower(string)说明：Convert string to lower case 转换字符串为小写例子：bit_length(jose) = 32函数：octet_length(string)说明：Number of bytes in string 计算字符串的字节数例子：octet_length(jose) = 4函数：overlay(string placing string from int [for int])说明：Replace substring 替换字符串中任意长度的子字串为新字符串例子：overlay(Txxxxas placing hom from 2 for 4) = 4函数：position(substring in string)说明：Location of specified substring 子串在一字符串中的位置例子：position(om in Thomas) = 3函数：substring(string [from int] [for int])说明：Extract substring 截取任意长度的子字符串例子：substring(Thomas from 2 for 3) = hom函数：substring(string from pattern)说明：Extract substring matching POSIX regular expression. See Section 9.7 for more information on pattern matching. 利用正则表达式对一字符串进行任意长度的字串的截取例子：substring(Thomas from ...$) = mas函数：substring(string from pattern for escape)说明：Extract substring matching SQL regular expression. See Section 9.7 for more information on pattern matching. 利于正则表达式对某类字符进行删除，以得到子字符串例子：trim(both x from xTomxx) = Tom函数：trim([leading | trailing | both] [characters] from string)?说明：Remove the longest string containing only the characters (a space by default) from the start/end/both ends of the string 去除尽可能长开始，结束或者两边的某类字符，默认为去除空白字符，当然可以自己指定，可同时指定多个要删除的字符串例子：trim(both x from xTomxx) = Tom函数：upper(string)说明：Convert string to uppercase 将字符串转换为大写例子：upper(tom) = TOM函数：ascii(string)说明：ASCII code of the first character of the argument. For UTF8 returns the Unicode code point of the character. For other multibyte encodings.the argument must be a strictly ASCII character. 得到某一个字符的Assii值例子：ascii(x) = 120函数：btrim(strin