如何从Postgres中的字符串中提取特定单词

Question

产品名称包含由空格分隔的单词。 第一个字是品牌等的第二个字。

如何从字符串中提取这些单词，eq如何实现如下查询：

select
  id,       
  getwordnum( prodname,1 ) as size,
  getwordnum( prodname,2 ) as brand
  from products
where ({0} is null or getwordnum( prodname,1 )={0} ) and
    ({1} is null or getwordnum( prodname,2 )={1} )


create table product ( id char(20) primary key, prodname char(100) );

如何在Postgres中创建getwordnum（）函数或者是否应该在此查询中直接使用某些substring（）或其他函数来提高速度？

Answer 1

您可以尝试使用函数split_part

select
  id,       
  split_part( prodname, ' ' , 1 ) as size,
  split_part( prodname, ' ', 2 ) as brand
  from products
where ({0} is null or split_part( prodname, ' ' , 1 )= {0} ) and
    ({1} is null or split_part( prodname, ' ', 2 )= {1} )

Answer 2

您正在寻找的可能是split_part ，它可以作为PostgreSQL中的String函数使用。 见http://www.postgresql.org/docs/9.1/static/functions-string.html 。

Answer 3

select
    id,       
    prodname[1] as size,
    prodname[2] as brand
from (
    select
        id,
        regexp_split_to_array(prodname, ' ') as prodname
    from products
) s
where
    ({0} is null or prodname[1] = {0})
    and
    ({1} is null or prodname[2] = {1})