MySQL：使用 id 将 table2 中的条目与 table1 中的条目匹配，然后将匹配项作为新列插入 table2

Question

Suppose I have two datasets of students. I want to match students in one dataset to another. The match criteria is whether the first 4 letters of the first name, last 4 letters of last name, and the first 4 letters of the first word in the high school name match. If these are all true, we assume that the students are the same.

I am able to accomplish this using

SELECT t1.`Full Name`, t1.`uid_hist`, t2.`fullname`, t2.`hsname`, t1.`High School`
FROM table1 t1
LEFT JOIN table2 t2
on SUBSTRING(REGEXP_SUBSTR(LOWER(t2.fullname), '^[a-z]*?[^a-z]'), 1, 4) = SUBSTRING(REGEXP_SUBSTR(LOWER(t1.`Full Name`), '^[a-z]*?[^A-z]'), 1, 4)
and SUBSTRING(REGEXP_SUBSTR(LOWER(t2.fullname), '[^a-z][a-z]*?$'), -4) = SUBSTRING(REGEXP_SUBSTR(LOWER(t1.`Full Name`), '[^a-z][a-z]*?$'), -4)
and SUBSTRING(REGEXP_SUBSTR(LOWER(t2.hsname), '^[a-z]*?[^a-z]'), 1, 4) = SUBSTRING(REGEXP_SUBSTR(LOWER(t1.`High School`), '^[a-z]*?[^a-z]'), 1, 4) 

This is pretty slow, so I am also curious if there is a better way, but it appears to work as intended.

Now, my question is, how do I go about inserting the matched 'uid's from table 1 as a new column in table2? That is, if there is a student who was matched to a student in table1, then the unique identifier for that student in table1 will be in the column 'match'. For students that are not matched, 'match' will simply be null.

If a row in table2 is matched to more than one student in table1, let's say we repeat the row in table2, except with different values for 'match'.

Is there any straightforward way to accomplish this? I am very new to MySQL and not sure how to proceed

Answer 1

I don't think you need regular expressions for this:

SELECT t1.`Full Name`, t1.`uid_hist`, t2.`fullname`, t2.`hsname`, t1.`High School`
FROM table1 t1 LEFT JOIN
     table2 t2
     ON LEFT(t2.fullname, 4) = LEFT(LOWER(t1.`Full Name`) AND
        RIGHT(t2.fullname, 4) = RIGHT(LOWER(t1.`Full Name`) AND
        LEFT(t2.`High School`, 4) = LEFT(LOWER(t1.`High School`)