Oracle SQL Developer中的SQL查询

Question

I have four tables that I want to join and display the output all together. I'm not sure how the syntax works for Oracle SQL Developer. I know this is an easy question for a programmer and I was hoping someone can make a suggestion on how the code might look like.

The tables are tables are: JNL1 JNL2 JNL3 JNL4

JNL1
JNL2
JNL3
JNL4

I only want to display the results with UserCode=Automation and the Date to be one day before the current one. The code for that is:

  UserCode = 'Automation' AND     
  CONVERT(VARCHAR,LEFT(DATE,8))=CONVERT(VARCHAR(8),GETDATE()-1,112)

The keys that are common between all four of these tables is ItemID, Date, and UserCode.

I'm not sure how the query will look like, I can generate the joining tables query and the UserCode/Date query as separate queries. But when I combine them into one query I either get errors on ambiguous column name, or the query runs with no data being displayed from the database.

Answer 1

Don't join the tables. as you require to get the data from only one table and table structure are same then you can have multiple unions

-- In oracle database you can not have column name as date, I am assuming that date column name is c_date-

select ItemID, c_Date, and UserCode
from Jul1
where UserCode = 'Automation' 
  AND c_date = trunc(sysdate) -1
union all 
select ItemID, c_Date, and UserCode
from Jul2
where UserCode = 'Automation' 
  AND c_date = trunc(sysdate) -1
union all 
select ItemID, c_Date, and UserCode
from Jul3
where UserCode = 'Automation' 
  AND c_date = trunc(sysdate) -1
union all 
select ItemID, c_Date, and UserCode
from Jul4
where UserCode = 'Automation' 
  AND c_date = trunc(sysdate) -1

* sysdate is system function which will return the current date with time value.