符号的含义? {} [] <> | ::= ,...n

2002-07-26 09:10:18 479 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

R、Z、N、Q数集符号全解析：从数学含义到编程应用在数学与编程的交叉学习中，数集符号是不可回避的基础概念。自然数、整数、有理数、实数分别对应N、Z、Q、R，这些字母背后不仅藏着拉丁语和德语的历史渊源，更体现了数系扩张的深层逻辑：自然数满足计数需求，整数补全减法封闭，有理数解决除法问题，实数则填满数轴上的每一个缝隙。理解这些符号的定义与变形，如N*、Z⁺、R⁺，有助于在数学表达和代码类型系统中建立准确的抽象映射。无论是解析函数的定义域，还是处理浮点数精度误差，数集符号都能提供清晰的思维框架。本文从符号起源出发，结合封闭性原理、常见误区及Python数值类型，阅读详情

UPDATE
{
table_name WITH ( < table_hint_limited > [ ...n ] )
| view_name
| rowset_function_limited
}
SET
{ column_name = { expression | DEFAULT | NULL }
| @variable = expression
| @variable = column = expression } [ ,...n ]

{ { [ FROM { < table_source > } [ ,...n ] ]

[ WHERE
< search_condition > ] }
|
[ WHERE CURRENT OF
{ { [ GLOBAL ] cursor_name } | cursor_variable_name }
] }
[ OPTION ( < query_hint > [ ,...n ] ) ]

< table_source > ::=
table_name [ [ AS ] table_alias ] [ WITH ( < table_hint > [ ,...n ] ) ]
| view_name [ [ AS ] table_alias ]
| rowset_function [ [ AS ] table_alias ]
| derived_table [ AS ] table_alias [ ( column_alias [ ,...n ] ) ]
| < joined_table >

< joined_table > ::=
< table_source > < join_type > < table_source > ON < search_condition >
| < table_source > CROSS JOIN < table_source >
| < joined_table >

< join_type > ::=
[ INNER | { { LEFT | RIGHT | FULL } [OUTER] } ]
[ < join_hint > ]
JOIN

< table_hint_limited > ::=
{ FASTFIRSTROW
| HOLDLOCK
| PAGLOCK
| READCOMMITTED
| REPEATABLEREAD
| ROWLOCK
| SERIALIZABLE
| TABLOCK
| TABLOCKX
| UPDLOCK
}

< table_hint > ::=
{ INDEX ( index_val [ ,...n ] )
| FASTFIRSTROW
| HOLDLOCK
| NOLOCK
| PAGLOCK
| READCOMMITTED
| READPAST
| READUNCOMMITTED
| REPEATABLEREAD
| ROWLOCK
| SERIALIZABLE
| TABLOCK
| TABLOCKX
| UPDLOCK
}

< query_hint > ::=
{ { HASH | ORDER } GROUP
| { CONCAT | HASH | MERGE } UNION
| {LOOP | MERGE | HASH } JOIN
| FAST number_rows
| FORCE ORDER
| MAXDOP
| ROBUST PLAN
| KEEP PLAN
}

m$开发文档中有这些表达式，也就是这个命令的详细用法，但是我从没看过有关里面符号含义的文档. 比如{} [] <> | ::= ,...n
请大家解释一下，最好提供一下详细的网址有这些说明：)

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