SqlServer常用的语法

-- SQL创建联合唯一索引的语法

-- Create a nonclustered index on a table or view
CREATE INDEX i1 ON t1 (col1);

-- Create a clustered index on a table and use a 3-part name for the table
CREATE CLUSTERED INDEX i1 ON d1.s1.t1 (col1);

-- Syntax for SQL Server and Azure SQL Database
-- Create a nonclustered index with a unique constraint
-- on 3 columns and specify the sort order for each column
CREATE UNIQUE INDEX i1 ON t1 (col1 DESC, col2 ASC, col3 DESC);

-- 快速查看表结构

1.sp_help table_name;           

如： [sql] sp_help Student;

2.sp_columns table_name;

如： [sql] sp_columns Student;

--merge的用法（待openJson with的语法）

DECLARE @json VARCHAR(max) = '{
    "employeeId": 1,
    "createTime": "2020-04-09 16:35:12"
}';
  
MERGE dbo.tEmployeeEmergencyContact AS t -- 需要操作的主体表
USING
(SELECT * FROM OPENJSON(@json) WITH (employeeId BIGINT) ) AS s (employeeId) -- USING里面是数据源，as以后，必须按照顺序指定字段名
ON t.employeeId = s.employeeId -- 这里是对比的条件
WHEN MATCHED THEN
    -- 如果有匹配就更新,只用写要更新的内容即可
    UPDATE SET t.emergencyContact = '张三',
               t.emergencyPhone = '18621704425',
               t.modifyTime = GETDATE(),
               t.modifierName = 'system' 
			   
WHEN NOT MATCHED THEN
    -- 没有匹配就新增,注意这里的INSERT不能再跟表名了
    INSERT
    (
        employeeId,
        emergencyContact,
        emergencyPhone,
        creatorName,
        createTime,
        modifierName,
        modifyTime,
        isDel
    )
    VALUES
    (1, '张三', '18621704425', 'system', GETDATE(), 'system', GETDATE(),  0);
-- merge必须分号结尾,不然报错

 

--开启/关闭数据库的执行时间（可以看到执行的时间精确到毫秒）

SET STATISTICS TIME ON 
SET STATISTICS TIME OFF

 

-- 查看表结构（可以直接粘贴到Excel）

 

SELECT
     表名       = Case When A.colorder=1 Then D.name Else '' End,
     表说明     = Case When A.colorder=1 Then isnull(F.value,'') Else '' End,
     字段序号   = A.colorder,
     字段名     = A.name,
     字段说明   = isnull(G.[value],''),
     标识       = Case When COLUMNPROPERTY( A.id,A.name,'IsIdentity')=1 Then '√'Else '' End,
     主键       = Case When exists(SELECT 1 FROM sysobjects Where xtype='PK' and parent_obj=A.id and name in (
                      SELECT name FROM sysindexes WHERE indid in( SELECT indid FROM sysindexkeys WHERE id = A.id AND colid=A.colid))) then '√' else '' end,
     类型       = B.name,
     占用字节数 = A.Length,
     长度       = COLUMNPROPERTY(A.id,A.name,'PRECISION'),
     小数位数   = isnull(COLUMNPROPERTY(A.id,A.name,'Scale'),0),
     允许空     = Case When A.isnullable=1 Then '√'Else '' End,
     默认值     = isnull(E.Text,'')
 FROM
     syscolumns A
 Left Join
     systypes B
 On
     A.xusertype=B.xusertype
 Inner Join
     sysobjects D
 On
     A.id=D.id  and D.xtype='U' and  D.name<>'dtproperties'
 Left Join
     syscomments E
 on
     A.cdefault=E.id
 Left Join
 sys.extended_properties  G
 on
     A.id=G.major_id and A.colid=G.minor_id
 Left Join

 sys.extended_properties F
 On
     D.id=F.major_id and F.minor_id=0
     where d.name  IN(
	 '表名'

	 )    --如果只查询指定表,加上此条件
 Order By
     A.id,A.colorder;