SQL asks how to merge two tables.

First, use the left join to completely find out the 1 table, then use the right join to completely find out the 2 tables, and finally merge the results.

select as number ,t1name as name , as subject 1 score ,case when is null then 0 else end as subject 2 score

from t1 left join t2 onunionselect as number ,t2name as name ,case when is null then 0 else end as subject 1 score , as subject 2 score

from t1 right join t2 on ;

Hehe. There is no information. It's going to be hard. The user's information should be found. and how it is exported.

Or strings this file to see if there's any useful information.

1. The first is to use a temporary table to put all the data in one table.

insert into qunlist select * from qunlist89,90,91,92;

Then query in the qunlist.

2. The second way is to use the union all way to query.

select * from qunlist89union all

select * from qunlist90;

Preferably, you should merge the data in Table 1, Table 2, and Table 3 into a table and use Union All to merge them together. Ignore whether the names are duplicated or not.

However, when performing the merger, it is necessary to put a label on each data to be merged, representing the data from which table this is, and this label is finally used to distinguish the different scores of the same person.

The merged data is converted from row to column.

select a.Entrant's name, bLong-distance running score, cSwimming score, dHigh Jump Score from (

select Participant Name from (.

Select Participant's Name from Table 1

UnionSelect Participant Name from Table 2 UnionSelect Participant Name from Table 3) as t) as a

Left join Table 1 as b

on a.Entrant's name, bEntrant's name.

Left join Table 2 as c

on a.Participant's name = cEntrant's name.

Left join Table 3 as d

on a.Participant's name = dEntrant's name.

1. First, use a temporary table to insert all the data into qunlist select * from qunlist89,90,91,92;

Then query in the qunlist.

2. Second, use the union all method to query select * from qunlist89union all

select * from qunlist90;

The first way is to use a temporary table, insert into qunlist select * from qunlist89,90,91,92;

Then query in the qunlist.

The second way is to use the union all way to query.

select * from qunlist89union all

select * from qunlist90;