【参数说明】
data_type(length) 规定目标数据类型（带有可选的长度）。
expression 规定需要转换的值。
style 规定日期/时间的输出格式。
【示例】
--查询日期为2023年6月的数据
select * from 表 where Convert(varchar(7),字段,25) = '2023-06';
实用方法
--查询数据库的所有的表
select name from sys.tables;
--查询数据库的所有表及视图
select table_name from information_schema.tables;
数据字典
SELECT
CASE WHEN col.colorder = 1 THEN obj.name ELSE '' END AS 表名,
col.colorder AS 序号 ,
col.name AS 列名 ,
ISNULL(ep.[value], '') AS 列说明 ,
t.name AS 数据类型 ,
col.length AS 长度 ,
ISNULL(COLUMNPROPERTY(col.id, col.name, 'Scale'), 0) AS 小数位数 ,
CASE WHEN COLUMNPROPERTY(col.id, col.name, 'IsIdentity') = 1 THEN '√' ELSE '' END AS 标识 ,
CASE WHEN EXISTS (SELECT 1 FROM dbo.sysindexes si
INNER JOIN dbo.sysindexkeys sik ON si.id = sik.id AND si.indid = sik.indid
INNER JOIN dbo.syscolumns sc ON sc.id = sik.id AND sc.colid = sik.colid
INNER JOIN dbo.sysobjects so ON so.name = si.name AND so.xtype = 'PK'
WHERE sc.id = col.id AND sc.colid = col.colid ) THEN '√' ELSE '' END AS 主键 ,
CASE WHEN col.isnullable = 1 THEN '√' ELSE '' END AS 允许空 ,
ISNULL(comm.text, '') AS 默认值
FROM dbo.syscolumns col
LEFT JOIN dbo.systypes t ON col.xtype = t.xusertype
inner JOIN dbo.sysobjects obj ON col.id = obj.id AND obj.xtype = 'U' AND obj.status >= 0
LEFT JOIN dbo.syscomments comm ON col.cdefault = comm.id
LEFT JOIN sys.extended_properties ep ON col.id = ep.major_id AND col.colid = ep.minor_id AND ep.name = 'MS_Description'
LEFT JOIN sys.extended_properties epTwo ON obj.id = epTwo.major_id AND epTwo.minor_id = 0 AND epTwo.name = 'MS_Description'
WHERE obj.name in(select name from sys.tables) --查询当前数据库所有表名
order by obj.name
