SQL中的“：1”，“：2”是什么意思？

Question

I am looking at a sql statement that looks like this:

...
AND col2_.col_date >= :1
AND col2_.col_date <= :2
...

and I have no idea what :1 and :2 does??

Can someone enlighten me,

Thanks, :)

Answer 1

它们是参数化查询中的占位符，等待程序出现并提供参数。

Answer 2

There are parameters, specified when running the query - rather than having the date as text directly in the query, they're parameters injected when the query is run. What you're seeing are the first and second placeholders...the syntax varies between servers and providers. For example sometimes you'll see them names instead of numbered, etc.

Answer 3

These are placeholders, but not in SQL, only in your programming language that constructs the SQL-string. In SQL (PostgreSQL anyway) you have to use numbered placeholders $1, $2, etc. Check the PostgreSQL-manual for PREPARE or the PHP-manual for pg_query_params() .