1

select '123'+'456';

1

2

3

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

或

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

1

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

1

2

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”

1

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

1

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

1

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。”

1

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

1

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

1

2

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

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

1

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

1

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

1

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

1

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