在mysql和php中合并两个表的更有效方法？

Question

I have two tables that contain similar information. As a minimal example say I have the following:

table1  id|date|info1
table2  id|date|info2

I want to merge these two tables into one such that it becomes

table3 id|date|info1|info2

I tried the following:

SELECT table1.id,table1.date,table1.info1,table2.info2
FROM table1 as temp1
JOIN table2 as temp2
ON table1.id=table2.id AND table1.date=table2.date

then loop through this selection and update accordingly.

It works, but is very slow. I was wondering whether there was a better way to do this.

Answer 1

You can use CTAS (Create Table As Select) like this:

CREATE TABLE YourMergedTable AS
SELECT table1.id,table1.date,table1.info1,table2.info2
FROM table1 as temp1
JOIN table2 as temp2
ON table1.id=table2.id AND table1.date=table2.date

MySQL will detect the types of the fields that result from the query, and make a table structure accordingly.

If you already have a table, or you want to create it explicitly for any other reason, you can still insert records like that:

INSERT INTO YourMergedTable(ID, Date, Info1, Info2) /* These are the fieldnames in the  table */
SELECT table1.id,table1.date,table1.info1,table2.info2
FROM table1 as temp1
JOIN table2 as temp2
ON table1.id=table2.id AND table1.date=table2.date

Answer 2

This will produce the result as id|date|info1|info2

    SELECT id, date, info1 AS info1, NULL AS info2 FROM table1
    UNION
    SELECT id, date, NULL AS info1, info2 AS info2 FROM table2

To insert the results into a table3 you can do

    INSERT INTO table3
    SELECT id, date, info1 AS info1, NULL AS info2 FROM table1
    UNION
    SELECT id, date, NULL AS info1, info2 AS info2 FROM table2