SELECT SUBSTRING('123456', 2, 3); --'234'
SELECT LEFT('123456', 3); --'123'
SELECT RIGHT('123456', 3); --'456'
SELECT LEN('你好'); --2
SELECT DATALENGTH('你好'); --4
SELECT CHARINDEX('23', '1234553'); --2
SELECT PATINDEX('%[0-9]%','abc123gh'); --4
SELECT REPLACE('1-1', '-', '.'); --'1.1'
SELECT REPLICATE('A', 4); --'AAAA'
SELECT STUFF('ABC', 2, 0, 'abc'); --'AabcBC'
SELECT UPPER('AbCd'); --'ABCD'
SELECT LOWER('AbCd'); --'abcd'
SELECT RTRIM(' abcd '); --' abcd'
SELECT LTRIM(' abcd '); --'abcd '
