select 

    max(age) max_age, 

    min(age) min_age, 

    count(age) count_age, 

    avg(age) avg_age, 

    sum(age) sum_age, 

    var(age) var_age 

from student;

select dateAdd(day, 3, getDate());--加天

select dateAdd(year, 3, getDate());--加年

select dateAdd(hour, 3, getDate());--加小时

--返回跨两个指定日期的日期边界数和时间边界数

select dateDiff(day, '2011-06-20', getDate());

--相差秒数

select dateDiff(second, '2011-06-22 11:00:00', getDate());

--相差小时数

select dateDiff(hour, '2011-06-22 10:00:00', getDate());

select dateName(month, getDate());--当前月份

select dateName(minute, getDate());--当前分钟

select dateName(weekday, getDate());--当前星期

select datePart(month, getDate());--当前月份

select datePart(weekday, getDate());--当前星期

select datePart(second, getDate());--当前秒数

select day(getDate());--返回当前日期天数

select day('2011-06-30');--返回当前日期天数

select month(getDate());--返回当前日期月份

select month('2011-11-10');

select year(getDate());--返回当前日期年份

select year('2010-11-10');

select getDate();--当前系统日期

select getUTCDate();--utc日期

select pi();--PI函数

select rand(100), rand(50), rand(), rand();--随机数

select round(rand(), 3), round(rand(100), 5);--精确小数位

--精确位数，负数表示小数点前

select round(123.456, 2), round(254.124, -2);

select round(123.4567, 1, 2);

select col_name(object_id('student'), 1);--返回列名

select col_name(object_id('student'), 2);

--该列数据类型长度

select col_length('student', col_name(object_id('student'), 2)); 

--该列数据类型长度

select col_length('student', col_name(object_id('student'), 1)); 

--返回类型名称、类型id

select type_name(type_id('varchar')), type_id('varchar');

--返回列类型长度

select columnProperty(object_id('student'), 'name', 'PRECISION');

--返回列所在索引位置

select columnProperty(object_id('student'), 'sex', 'ColumnId');

select ascii('a');--字符转换ascii值

select ascii('A');

select char(97);--ascii值转换字符

select char(65);

select nchar(65);

select nchar(45231);

select nchar(32993);--unicode转换字符

select unicode('A'), unicode('中');--返回unicode编码值

select soundex('hello'), soundex('world'), soundex('word');

select patindex('%a', 'ta'), patindex('%ac%', 'jack'), patindex('dex%', 'dexjack');--匹配字符索引

select 'a' + space(2) + 'b', 'c' + space(5) + 'd';--输出空格

select charIndex('o', 'hello world');--查找索引

select charIndex('o', 'hello world', 6);--查找索引

select quoteName('abc[]def'), quoteName('123]45');

--精确数字

select str(123.456, 2), str(123.456, 3), str(123.456, 4);

select str(123.456, 9, 2), str(123.456, 9, 3), str(123.456, 6, 1), str(123.456, 9, 6);

select difference('hello', 'helloWorld');--比较字符串相同

select difference('hello', 'world');

select difference('hello', 'llo');

select difference('hello', 'hel');

select difference('hello', 'hello');

select replace('abcedef', 'e', 'E');--替换字符串

select stuff('hello world', 3, 4, 'ABC');--指定位置替换字符串

select replicate('abc#', 3);--重复字符串

select subString('abc', 1, 1), subString('abc', 1, 2), subString('hello Wrold', 7, 5);--截取字符串

select len('abc');--返回长度

select reverse('sqlServer');--反转字符串

select left('leftString', 4);--取左边字符串

select left('leftString', 7);

select right('leftString', 6);--取右边字符串

select right('leftString', 3);

select lower('aBc'), lower('ABC');--小写

select upper('aBc'), upper('abc');--大写

--去掉左边空格

select ltrim(' abc'), ltrim('# abc#'), ltrim('  abc');

--去掉右边空格

select rtrim(' abc    '), rtrim('# abc#   '), rtrim('abc');

select current_user;

select user;

select user_id(), user_id('dbo'), user_id('public'), user_id('guest');

select user_name(), user_name(1), user_name(0), user_name(2);

select session_user;

select suser_id('sa');

select suser_sid(), suser_sid('sa'), suser_sid('sysadmin'), suser_sid('serveradmin');

select is_member('dbo'), is_member('public');

select suser_name(), suser_name(1), suser_name(2), suser_name(3);

select suser_sname(), suser_sname(0x01), suser_sname(0x02), suser_sname(0x03);

select is_srvRoleMember('sysadmin'), is_srvRoleMember('serveradmin');

select permissions(object_id('student'));

select system_user;

select schema_id(), schema_id('dbo'), schema_id('guest');

select schema_name(), schema_name(1), schema_name(2), schema_name(3);

select app_name();--当前会话的应用程序名称

select cast(2011 as datetime), cast('10' as money), cast('0' as varbinary);--类型转换

select convert(datetime, '2011');--类型转换

select coalesce(null, 'a'), coalesce('123', 'a');--返回其参数中第一个非空表达式

select collationProperty('Traditional_Spanish_CS_AS_KS_WS', 'CodePage');

select current_timestamp;--当前时间戳

select current_user;

select isDate(getDate()), isDate('abc'), isNumeric(1), isNumeric('a');

select dataLength('abc');

select host_id();

select host_name();

select db_name();

select ident_current('student'), ident_current('classes');--返回主键id的最大值

select ident_incr('student'), ident_incr('classes');--id的增量值

select ident_seed('student'), ident_seed('classes');

select @@identity;--最后一次自增的值

select identity(int, 1, 1) as id into tab from student;--将studeng表的烈属，以/1自增形式创建一个tab

select * from tab;

select @@rowcount;--影响行数

select @@cursor_rows;--返回连接上打开的游标的当前限定行的数目

select @@error;--T-SQL的错误号

select @@procid;

set datefirst 7;--设置每周的第一天，表示周日

select @@datefirst as '星期的第一天', datepart(dw, getDate()) AS '今天是星期';

select @@dbts;--返回当前数据库唯一时间戳

set language 'Italian';

select @@langId as 'Language ID';--返回语言id

select @@language as 'Language Name';--返回当前语言名称

select @@lock_timeout;--返回当前会话的当前锁定超时设置（毫秒）

select @@max_connections;--返回SQL Server 实例允许同时进行的最大用户连接数

select @@MAX_PRECISION AS 'Max Precision';--返回decimal 和numeric 数据类型所用的精度级别

select @@SERVERNAME;--SQL Server 的本地服务器的名称

select @@SERVICENAME;--服务名

select @@SPID;--当前会话进程id

select @@textSize;

select @@version;--当前数据库版本信息

select @@CONNECTIONS;--连接数

select @@PACK_RECEIVED;

select @@CPU_BUSY;

select @@PACK_SENT;

select @@TIMETICKS;

select @@IDLE;

select @@TOTAL_ERRORS;

select @@IO_BUSY;

select @@TOTAL_READ;--读取磁盘次数

select @@PACKET_ERRORS;--发生的网络数据包错误数

select @@TOTAL_WRITE;--sqlserver执行的磁盘写入次数

select patIndex('%soft%', 'microsoft SqlServer');

select patIndex('soft%', 'software SqlServer');

select patIndex('%soft', 'SqlServer microsoft');

select patIndex('%so_gr%', 'Jsonisprogram');

--查询所有已创建函数

select definition,* from sys.sql_modules m join sys.objects o on m.object_id = o.object_id

and type in('fn', 'if', 'tf');

if (object_id('fun_add', 'fn') is not null)

    drop function fun_add

go

create function fun_add(@num1 int, @num2 int)

    returns int

with execute as caller

as

    begin

        declare @result int;

        if (@num1 is null)

            set @num1 = 0;

        if (@num2 is null)

            set @num2 = 0;

        set @result = @num1 + @num2;

        return @result;

    end

go

调用函数

select dbo.fun_add(id, age) from student;

--自定义函数，字符串连接

if (object_id('fun_append', 'fn') is not null)

    drop function fun_append

go

create function fun_append(@args nvarchar(1024), @args2 nvarchar(1024))

    returns nvarchar(2048)

as

    begin

        return @args + @args2;

    end

go

select dbo.fun_append(name, 'abc') from student;

alter function fun_append(@args nvarchar(1024), @args2 nvarchar(1024))

    returns nvarchar(1024)

as

    begin

        declare @result varchar(1024);    

        --coalesce返回第一个不为null的值    

        set @args = coalesce(@args, '');

        set @args2 = coalesce(@args2, '');;

        set @result = @args + @args2;

        return @result;

    end

go

select dbo.fun_append(name, '#abc') from student;

--返回table对象函数

select name, object_id, type from sys.objects where type in ('fn', 'if', 'tf') or type like '%f%';

if (exists (select * from sys.objects where type in ('fn', 'if', 'tf') and name = 'fun_find_stuRecord'))

    drop function fun_find_stuRecord

go

create function fun_find_stuRecord(@id int)

    returns table

as

    return (select * from student where id = @id);

go

select * from dbo.fun_find_stuRecord(2);