查询选择（LEFT JOIN）[关闭]

Question

the questions, why example 1 works and example 2 doesn't I want to use the second variant

example1

$query = "SELECT i.category_id, h.line
FROM litline i 
LEFT JOIN links as h ON (i.category_id = h.id)"; 

example 2

$query = "SELECT i.category, h.line
FROM litline i 
LEFT JOIN links as h ON (i.category = h.name)"; 

please any suggestions, thanks

Answer 1

In the second query you have at the end an single quote, but at the beginning double one.