MySQL Self-study chapter (ix)--string function (ii)

（8) to delete the function of the specified stringTRIM (S1 from S)

TRIM (S1 from S2) deletes all substrings in the string s s1. S1 is optional, and when unspecified, removes spaces.

Select Trim (' xy ' from ' xyxboxyokxxyxy ');

(9) function for repeating string generationREPEAT (s,n)

Returns a string consisting of a repeating string s , and the number of s is n. If n<0, returns an empty string. returns null if s or n is null

Select repeat (' MySQL ', 3);

（Ten) space functionSPACE (n)and replace functionsREPLACE (S,S1,S2)

Space (n) returns a string consisting of n spaces.

Select Concat (' (', Space (6), ') ');

Select replace (' xxx.mysql.com ', ' x ', ' W ');

（ Onea function that compares the size of a stringSTRCMP (S1,S2)

Returns 0if two strings are equal,or 1if s1<s2returns 1

Select strcmp (' AA ', ' AA '), strcmp (' abc ', ' ACB '), strcmp (' ACB ', ' abc ');

(12) Get the SUBSTRING function substring (s,n,len)and theMID (S,n.len)

SUBSTRING (S,n,len) returns a substring of length len that was searched from n position . MID (s,n.len) acts the same as the former.

Select substring (' ABCDEFG ', 4, 3);

Select mid (' ABCDEFG ', 2,2);

(13) function to match the starting position of a substring

LOCATE (STR1,STR),POSITION (str1 in str2) and INSTR (STR,STR1) 3 functions are the same. Returns the starting position of the substring str1 in the string str

Select locate (' Ball ', ' football '), position (' ball ' in ' Football '), InStr (' Football ', ' Ball ');

(14) Inverse string function reverse (s)

Select reverse (' 12345 ');

(15) Returns a string function at the specified position

ELN (N, string 1, string 2, string 3 ... string N) if n=1 , the return value is a string 1 , if n=2 , returns a string 2 ...

Select ELT (3, ' 123 ', ' abc ', ' 456 ', ' def ');

(16) Returns the location of the specified string in the return field (S,S1,S2...)

Select field (' 123 ', ' abc ', ' 123 ');

(17) function Find_in_set (S1,S2) to return substring position

Returns the position where the string S1 appears in the string s2 .

Select Find_in_set (' 123 ', ' abcd,1234,efg,123 ');

MySQL Self-study chapter (ix)--string function (ii)