4.1.3. Operators

4.1.3. Operators

4.1.3. 操作符

An operator name is a sequence of up to NAMEDATALEN-1 (63 by default) characters from the following list:

运算符名称是含以下列表中最多NAMEDATALEN-1（默认为63）个字符的序列：

+ - * / < > = ~ ! @ # % ^ & | ` ?

There are a few restrictions on operator names, however:

• -- and /* cannot appear anywhere in an operator name, since they will be taken as the start of a comment.

• A multiple-character operator name cannot end in + or -, unless the name also contains at least one of these characters:

但是，对运算符名称有一定的限制：

• 运算符名称中不能出现--和/*，因为它们会被认为是备注的一部分。

• 多字符运算符名称不能以+或-结尾，除非名称也包含以下至少一个字符：

~ ! @ # % ^ & | ` ?

For example, @- is an allowed operator name, but *- is not. This restriction allows PostgreSQL to parse SQL-compliant queries without requiring spaces between tokens.

例如，@-是一个可用的运算符名称，但是*-不是。 此限制使PostgreSQL可以解析与SQL兼容的查询，而无需在标记之间使用空格。

When working with non-SQL-standard operator names, you will usually need to separate adjacent operators with spaces to avoid ambiguity. For example, if you have defined a left unary operator named @, you cannot write X*@Y; you must write X* @Y to ensure that PostgreSQL reads it as two operator names not one.

在使用非SQL标准的运算符名称时，通常需要用空格分隔相邻的运算符，以避免产生歧义。 例如，如果定义了名为@的左一元运算符，则不能编写X*@Y； 您必须编写X*  @Y以确保PostgreSQL将其读取为两个运算符名称，而不是一个。