Table of contents
2. insert (str, x, y, instr) function:
3. The lower(str) and upper(str) functions:
4. Left(str,x) and right(str,x) functions:
5. lpad(str,n,pad) and rpad(str,n,pad) functions:
6. ltrim(str) and rtrim(str) functions:
7. The repeat(str,x) function:
11. substring (str, x, y) function:
1. concat function:
Concatenate the incoming parameters into a string
select concat('aaa', 'bbb', 'ccc') ,concat('aaa',null);
2. insert (str, x, y, instr) function:
Replace the string str starting with x string, y string length with instr
select INSERT('beijing2008you',12,3, 'me') ;
3. The lower(str) and upper(str) functions:
Replace all strings with uppercase or lowercase
select LOWER('BEIJING2008'), UPPER('beijing2008');
4. Left(str,x) and right(str,x) functions:
x characters from the far left (right) side of the string
SELECT LEFT('beijing2008',7),LEFT('beijing',null),RIGHT('beijing2008',4);
5. lpad(str,n,pad) and rpad(str,n,pad) functions:
Fill the leftmost (right) side of the string str with the string pad, knowing that the length is n characters long
SELECT LEFT('beijing2008',7),LEFT('beijing',null),RIGHT('beijing2008',4);
6. ltrim(str) and rtrim(str) functions:
Remove spaces from the left or right of the string str
select ltrim(' |beijing'),rtrim('beijing | ');
7. The repeat(str,x) function:
Returns the result of repeating str x times
select repeat('mysql ',3);
8. replace(str,a,b) function:
Replaces all occurrences of the string a in the string str with the string b
select replace('beijing_2010','_2010','2008');
9. trim (str) function:
Remove leading and trailing spaces from a string
10. strcmp(s1, s2) function:
Compare the magnitude of the ASCII code value of the string s1.s2 (-1,0,1)
select strcmp('a','b'),strcmp('b','b'),strcmp('c','b');
11. substring (str, x, y) function:
Returns a string of y characters long starting from position x of the string str
select substring('beijing2008',8,4),substring('beijing2008',1,7);
