从2个表中选择具有行作为具有相同ID的列的表

Question

I have 2 tables with various columns and the tokenid being the same for both. The second table has multiple rows with same tokenid and other columns are different.

Now, I need to select columns from both table where the token id is the same and in the second table, rows with same tokenid must be converted into columns.

Table1:

tokenid   acolumn1   acolumn2   acolumn4
   1       fname1     mname1     lname1
   2       fname2     mname2     lname2

Table2:

id   tokenid   bquestion   banswer
 1       1     questiona   answera
 2       1     questionb   answerb
 3       2     questiona   answera
 4       2     questionb   answerb
 5       3     questionc   answerc

The result should be

tokenid   acolumn1   acolumn2   acolumn3   bquestion1   banswer1   bquestion2   banswer2   bquestion3   banswer3
  1        fname1     mname1     lname1     questiona   answera    questionb    answerb    null           null  
  2        fname2     mname2     lname2     questiona   answera    questionb    answerb    questionc    answerc

I tried querying the second table first with distinct and used it as a subquery to join with the table1. But the database has more than 200,000 rows in table 2 and the match with a tokenid with selection by acolumn1 will produce about 20000 rows result. So my query doesnt complete. is there any optimized way to solve this?

PS: I'd like to add that I do the queries with php using pdo

Answer 1

Try this code this joins all columns of your table1 and table2.

SELECT table1.tokenid, table1.acol1, table1.acol2, table1.acol3, table2.bquestion, table2.banswer FROM table1
    INNER JOIN table2
    ON table1.tokenid=table2.tokenid