SQL查询以从表或表中选择数据

Question

I have 2 tables a and b.

Table a
I'd   name

Table b
I'd name address

Now I have one name which may be present in either in a table or in b table. So I have to write a single to select the I'd of the person based on name in plsql.

Answer 1

I think you can use UNION like this:

SELECT *
FROM (
    SELECT Id, name, address, 'b' as tableName
    FROM b
    UNION ALL
    SELECT Id, name , '', 'a'
    FROM a) dt
WHERE name = yourName;

To have aa preview of the result: [SQL Fiddle]

You also have name of the table in tableName column.

Answer 2

select name from table_a where id = <id>
union
select name from table_b where id = <id>

or

select id from table_a where name = 'john'
union
select id from table_b where name = 'john'

This will get you the name from either table a or table b.