sql-server数据库语句学习

select name from master..Sysdatabases order by name;

select name from sysobjects where xtype = ‘U‘  ORDER BY name 

SELECT (case when a.colorder=1 then d.name else null end) 表名,  
a.colorder 字段序号,a.name 字段名,
(case when COLUMNPROPERTY( a.id,a.name,‘IsIdentity‘)=1 then ‘√‘else ‘‘ end) 标识, 
(case when (SELECT count(*) FROM sysobjects  
WHERE (name in (SELECT name FROM sysindexes  
WHERE (id = a.id) AND (indid in  
(SELECT indid FROM sysindexkeys  
WHERE (id = a.id) AND (colid in  
(SELECT colid FROM syscolumns WHERE (id = a.id) AND (name = a.name)))))))  
AND (xtype = ‘PK‘))>0 then ‘√‘ else ‘‘ end) 主键,b.name 类型,a.length 占用字节数,  
COLUMNPROPERTY(a.id,a.name,‘PRECISION‘) as 长度,  
isnull(COLUMNPROPERTY(a.id,a.name,‘Scale‘),0) as 小数位数,(case when a.isnullable=1 then ‘√‘else ‘‘ end) 允许空,  
isnull(e.text,‘‘) 默认值,isnull(g.[value], ‘ ‘) AS [说明]
FROM  syscolumns a 
left join systypes b on a.xtype=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.class and f.minor_id=0
where b.name is not null
--WHERE d.name=‘要查询的表‘ --如果只查询指定表,加上此条件
order by a.id,a.colorder

--库操作
create database test;
use test;

--表操作
drop table Users;
create table users(id int,username char(100),password char(100),remarks char(100));

--数据操作
insert into Users values(1,‘admin‘,‘admin123‘,‘This is administrator for system‘);
update Users set username = ‘king‘,password = ‘123456‘ where username = ‘admin‘;
delete from Users where username = ‘king‘;
select * from Users;

select * from Users order by 1;

select LEN(username) from Users;