SQL中1总是等于'1'吗？

Question

我试图确定用于将数字与相同数字的字符或字符串版本进行比较的标准SQL行为.是否SELECT 1 = '1'(或类似)总是返回某种"truthy"值(true,1,'t'等)？我已经在PostgreSQL和MySQL上做了很多确认,但我找不到整个SQL的资源.

更新:问题的目的是我试图弄清楚在选择/插入/更新/等时使用不带引号的数字是否有效.来自非数字字段,其值为数字.

Answer 1

SELECT 1='1'给人TRUE因为'1'是一个正确的构造函数INT中知道我所有的实现.

但是SQL使用严格的输入,看到:

# SELECT 1=CAST('1' AS TEXT);
ERROR:  operator does not exist: integer = text
LINE 1: SELECT 1=CAST('1' AS TEXT);
                ^
HINT:  No operator matches the given name and argument type(s). You might need to add  explicit type casts.

关于标准(SQL 92,99和2003),它似乎是错误的:

     <literal> ::=
            <signed numeric literal>
          | <general literal>

     <general literal> ::=
            <character string literal>
          | <national character string literal>
          | <bit string literal>
          | <hex string literal>
          | <datetime literal>
          | <interval literal>

     <signed numeric literal> ::=
          [ <sign> ] <unsigned numeric literal>

     <unsigned numeric literal> ::=
            <exact numeric literal>
          | <approximate numeric literal>

     <exact numeric literal> ::=
            <unsigned integer> [ <period> [ <unsigned integer> ] ]
          | <period> <unsigned integer>

     <unsigned integer> ::= <digit>...

     <character string literal> ::=
          [ <introducer><character set specification> ]
          <quote> [ <character representation>... ] <quote>
            [ { <separator>... <quote> [ <character representation>... ] <quote> }... ]

因为<quote>只包含在<bit string literal>,<hex string literal>...中,但不包含在数字文字中......