在SQL中，双栏(||)是什么意思?(复制)

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• What does SQL Select symbol || mean? 6 answers
• SQL选择符号||是什么意思?6答案

I'm trying to understand the following query:
select count(distinct Name || '' || Surname) from PEOPLE;
What does the double bars mean? What does this query do?

我正在尝试理解以下查询:选择count(不同的名称|| ||姓氏);双杠是什么意思?这个查询做什么?

In MySQL:
select "aaaaa" || '' || "bbbbb";

在MySQL中，选择“aaaaa”||“||”bbb“bbb”;

+--------------------------+ | "aaaaa" || '' || "bbbbb" | +--------------------------+ | 0 | +--------------------------+

+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - + | |“五星级”|“| |”bbbbb“| + - - - - - - - - - - - - - - - - - - - - - - - - - + | 0 | + - - - - - - - - - - - - - - - - - - - - - - - - - +

1 个解决方案

#1

double bars are concatination:

双酒吧concatination:

select 'hello' || ' ' || 'world' from dual;

yields

收益率

'hello world'