这个语法如何理解？

-- =============================================
-- Create basic Instead Of Trigger
-- =============================================
IF EXISTS (SELECT name 
   FROM   sysobjects 
   WHERE  name = N'<trigger_name, sysname, trig_test>' 
   AND   type = 'TR')
    DROP TRIGGER <trigger_name, sysname, trig_test>
GO

CREATE TRIGGER <trigger_name, sysname, trig_test>
ON <table_or_view_name, sysname, pubs.dbo.sales>
INSTEAD OF INSERT
AS
BEGIN
RAISERROR (50009, 16, 10)
EXEC sp_who
END
GO

请问<trigger_name, sysname, trig_test>这个语法如何理解：<,>,trigger_name,sysname各代表什么？谢谢！ SQL
[解决办法]
单从字面意思看，trigger_name：触发器名、sysname：系统名
触发器语法：
Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger)
CREATE TRIGGER [ schema_name . ]trigger_name
ON { table
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view }
[ WITH <dml_trigger_option> [ ,...n ] ]
{ FOR
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AFTER
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INSTEAD OF }
{ [ INSERT ] [ , ] [ UPDATE ] [ , ] [ DELETE ] }
[ WITH APPEND ]
[ NOT FOR REPLICATION ]
AS { sql_statement [ ; ] [ ,...n ]
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EXTERNAL NAME <method specifier [ ; ] > }

<dml_trigger_option> ::=
[ ENCRYPTION ]
[ EXECUTE AS Clause ]

<method_specifier> ::=
assembly_name.class_name.method_name

Trigger on a CREATE, ALTER, DROP, GRANT, DENY, REVOKE, or UPDATE STATISTICS statement (DDL Trigger)
CREATE TRIGGER trigger_name
ON { ALL SERVER
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DATABASE }
[ WITH <ddl_trigger_option> [ ,...n ] ]
{ FOR
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AFTER } { event_type
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event_group } [ ,...n ]
AS { sql_statement [ ; ] [ ,...n ]

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EXTERNAL NAME < method specifier > [ ; ] }

<ddl_trigger_option> ::=
[ ENCRYPTION ]
[ EXECUTE AS Clause ]

<method_specifier> ::=
assembly_name.class_name.method_name

Trigger on a LOGON event (Logon Trigger)
CREATE TRIGGER trigger_name
ON ALL SERVER
[ WITH <logon_trigger_option> [ ,...n ] ]
{ FOR
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AFTER } LOGON
AS { sql_statement [ ; ] [ ,...n ]
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EXTERNAL NAME < method specifier > [ ; ] }
<logon_trigger_option> ::=
[ ENCRYPTION ]
[ EXECUTE AS Clause ]

<method_specifier> ::=
assembly_name.class_name.method_name


[解决办法]

-- ============================================= -- Create basic Instead Of Trigger -- ============================================= 
--判断是表中是否存在触发器
-- N'<trigger_name, sysname, trig_test>'： 触发器名称
IF EXISTS (SELECT name FROM sysobjects  WHERE  name = N'<trigger_name, sysname, trig_test>'       
 AND type = 'TR')    
 --如果存在则删除该触发器
 DROP TRIGGER <trigger_name, sysname, trig_test> 
 GO   
 --创建触发器
 -- <trigger_name, sysname, trig_test> ：触发器名称
 -- <table_or_view_name, sysname, pubs.dbo.sales> ：创建那张表或视图的触发器
 CREATE TRIGGER <trigger_name, sysname, trig_test> ON <table_or_view_name, sysname, pubs.dbo.sales> 
 --插入时触发
 INSTEAD OF INSERTASBEGIN   
 AS
 BEGIN
 --抛出一个错误
 RAISERROR (50009, 16, 10)  
    --sp_who可以返回如下信息： (可选参数LoginName, 或active代表活动会话数)
--Spid (系统进程ID)
--
--status (进程状态)
--
--loginame (用户登录名)
--
--hostname(用户主机名)
--
--blk (阻塞进程的SPID)
--
--dbname (进程正在使用的数据库名)
--
--Cmd (当前正在执行的命令类型)
   
 EXEC sp_who 
 END