MySQL LEFT JOIN with OR condition

Question

I have a tables :

table_a.date
2018-05-13 17:30:22
2018-05-13 17:30:22
2018-05-13 17:30:22

and :

table_b.date
2018-05-13 17:30:22
2018-05-13 17:30:23
2018-05-13 17:30:23

I need to LEFT JOIN these tables with condition : table_a.date = table_b.date , or table_a.date = table_b.date + 1 second .

more or less like this :

SELECT * 
FROM table_a
LEFT JOIN table_b
ON table_a.date = table_b.date OR table_a.date = table_b.date (+ 1 second)

but I have no idea how to use OR condition as requirement of LEFT JOIN . what is the right SQL for this?

Answer 1

Use the DATE_ADD as below:

SELECT * 
FROM table_a
LEFT JOIN table_b
ON table_a.date = table_b.date
OR table_a.date = date_add(table_b.date, interval 1 second)

Answer 2

为什么您需要检查秒，只需将两个日期都设置为相同的格式并检查（如果diff仅用于秒），请删除秒，请使用DATE_FORMAT(date, format_mask)

SELECT * FROM table_a LEFT JOIN table_b ON DATE_FORMAT(table_a.date, "%M %d %Y %h %i") = (table_a.date, "%M %d %Y %h %i")