我有一个带书名的表格,我想选择标题与正则表达式匹配的书籍,并按标题中正则表达式匹配的位置排序结果.
单词搜索很容易.例如.
TABLE book id title 1 The Sun 2 The Dead Sun 3 Sun Kissed
在将查询发送到DB之前,我将把.*放在客户端搜索词中的单词之间,所以我在这里用准备好的regexp编写sql.
SELECT book.id,book.title FROM book
WHERE book.title ~* '.*sun.*'
ORDER BY COALESCE(NULLIF(position('sun' in book.title),0),999999) ASC;
RESULT
id title
3 Sun Kissed
1 The Sun
2 The Dead Sun
但是如果搜索词有多个单词,我想匹配标题,这些标题包含搜索词中的所有单词和它们之间的任何内容,并按照之前的位置排序,所以我需要一个返回正则表达式位置的函数,我没有在Postgresql官方文档中找到合适的一个.
TABLE books
id title
4 Deep Space Endeavor
5 Star Trek: Deep Space Nine: The Never Ending Sacrifice
6 Deep Black: Space Espionage and National Security
SELECT book.id,book.title FROM book
WHERE book.title ~* '.*deep.*space.*'
ORDER BY ???REGEXP_POSITION_FUNCTION???('.*deep.*space.*' in book.title);
DESIRED RESULT
id title
4 Deep Space Endeavor
6 Deep Black: Space Espionage and National Security
5 Star Trek: Deep Space Nine: The Never Ending Sacrifice
我没有找到类似于??? REGEXP_POSITION_FUNCTION的任何功能???,你有什么想法吗？
执行此操作的一种方法(很多)：从匹配开始删除字符串的其余部分并测量截断字符串的长度：
原文链接：/postgresql/452768.htmlSELECT id,title FROM book WHERE title ILIKE '%deep%space%' ORDER BY length(regexp_replace(title,'deep.*space.*','','i'));
在WHERE子句中使用ILIKE,因为这通常更快(并且在这里也一样).
另请注意regexp_replace()函数(‘i’)的第四个参数,以使其不区分大小写.
备择方案
根据评论中的要求.
同时演示如何首先对匹配进行排序(和NULLS LAST).
SELECT id,title,substring(title FROM '(?i)(^.*)deep.*space.*') AS sub1,length(substring(title FROM '(?i)(^.*)deep.*space.*')) AS pos1,substring(title FROM '(?i)^.*(?=deep.*space.*)') AS sub2,length(substring(title FROM '(?i)^.*(?=deep.*space.*)')) AS pos2,substring(title FROM '(?i)^.*(deep.*space.*)') AS sub3,position((substring(title FROM '(?i)^.*(deep.*space.*)')) IN title) AS p3,regexp_replace(title,'i') AS reg4,length(regexp_replace(title,'i')) AS pos4 FROM book ORDER BY title ILIKE '%deep%space%' DESC NULLS LAST,'i'));
-> SQLfiddle展示全部.
