T_SQL语言的相关内容。

T-SQL是指Transact-SQL，是一种Microsoft SQL Server数据库管理系统中使用的SQL方言。它扩展了标准的SQL语言，支持过程化编程、变量定义、控制流程语句、事务处理、错误处理等。以下是一些T-SQL的常见用法和语法：

1. 创建表

CREATE TABLE table_name
(
  column1 datatype [NULL | NOT NULL],
  column2 datatype [NULL | NOT NULL],
  ...
)

2. 插入数据

INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);

3. 更新数据

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

4. 删除数据

DELETE FROM table_name
WHERE condition;

5. 选择数据

SELECT column1, column2, ...
FROM table_name
WHERE condition;

6. 创建存储过程

CREATE PROCEDURE procedure_name
AS
BEGIN
  -- procedure body
END

7. 变量定义

DECLARE @variable_name datatype;
SET @variable_name = value;

8. 控制流程语句

IF condition
BEGIN
  -- statements
END

WHILE condition
BEGIN
  -- statements
END

CASE expression
  WHEN value1 THEN result1
  WHEN value2 THEN result2
  ...
END

9. 事务处理

BEGIN TRANSACTION;
-- statements
COMMIT TRANSACTION;

BEGIN TRY
  BEGIN TRANSACTION;
  -- statements
  COMMIT TRANSACTION;
END TRY
BEGIN CATCH
  IF @@TRANCOUNT > 0
    ROLLBACK TRANSACTION;
END CATCH;

10. 错误处理

BEGIN TRY
  -- statements
END TRY
BEGIN CATCH
  -- error handling statements
END CATCH;