深入讲解SQL中的字符串拼接

select '123'+'456';

select '123'||'456' from dual;

select concat('123','456') from dual;

select concat('123','456');

SELECT id + place FROM Users WHERE id = 1; //提示错误“在将 varchar 值 'bzz' 转换成数据类型 int 时失败”
SELECT id + place FROM Users WHERE id = 5; //提示错误“在将 varchar 值 '102.34' 转换成数据类型 int 时失败”

SELECT id + place FROM Users WHERE id = 4; //返回int “105”

SELECT *, id + cost FROM Users WHERE id = 4 OR id = 5; //返回decimal “102.98”和“104.30”

SELECT *, place + cost FROM Users WHERE id = 1; //提示错误“从数据类型 varchar 转换为 numeric 时出错。”

SELECT *, uage + cost AS 'uage + cost' FROM Users

SELECT *, uname + place AS 'uname + place' FROM Users 

SELECT CAST('678' AS INT) + 123;
SELECT CONVERT(INT, '678') + 123;

SELECT *, CONVERT(varchar(10), id) + place FROM Users;

SELECT * FROM Users WHERE uname + place = 'aabzz';

SELECT * FROM Users WHERE uname = 'aa' AND place = 'bzz';

SELECT * FROM Users WHERE uname + 'rain@&%$man' + place = 'aa' + 'rain@&%$man' + 'bzz'