使用附加行添加和更新列/创建新表

Question

I have two huge tables with 10 million rows in table A and 2.5 million rows in table B. Both tables have a common field id. Table A has ~250 columns and table B has 5 columns. All the ids in table B are present in table A. I want to add a field (in date format) in table A to table B. I have two options, and both are taking lot of time to run. I want to know which will be efficient.

Option 1:
alter table B add column field date;
update B join A using(id) set a.field=b.field;

Option 2:
create table C as select a.*,b.field from B join A using(id);

id is indexed in both the tables and ENGINE is MyISAM.

Which option will be faster?

I think 2 because in option 1, adding a column is taking time, then while updating, lot of time is taken for the state copy to tmp table . In option 1, it straight away starts with the state 'Sending data'. Am I correct?

Also, can I do this in any other faster way?

Answer 1

If you only whant to select information you can create a view to get all the data together

CREATE VIEW 'my_view' as select * from B join A on B.id = A.id;

so you can run

select field,any_field from my_view where any_condition;

having duplicated data in a database is absolutly unrecommend

i hope this help you. sice it isnt any of your options.

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you can also run the query itself

 select  field,any_field from B join A on B.id = A.id where any_condition;