I have a data processor that would create a table from a select query.
<_config:table definition="CREATE TABLE TEMP_TABLE (PRODUCT_ID NUMBER NOT NULL, STORE NUMBER NOT NULL, USD NUMBER(20, 5),
CAD NUMBER(20, 5), Description varchar(5), ITEM_ID VARCHAR(256), PRIMARY KEY (ITEM_ID))" name="TEMP_TABLE"/>
and the select query is
<_config:query sql="SELECT DISTINCT ce.PRODUCT_ID, ce.STORE, op.USD ,op.CAD, o.Description, ce.ITEM_ID
FROM PRICE op, PRODUCT ce, STORE ex, OFFER o, SALE t
where op.ITEM_ID = ce.ITEM_ID and ce.STORE = ex.STORE
and ce.PRODUCT_ID = o.PRODUCT_ID and o.SALE_ID IN (2345,1234,3456) and t.MEMBER = ce.MEMBER"/>
When I run that processor, I get an unique constraint error, though I have a distinct in my select statement.
I tried with CREATE TABLE AS (SELECT .....) its creating fine.
Is it possible to get that error? I'm doing a batch execute so not able to find the individual record.
The select distinct applies to the entire row, not to each column individually. So, two rows could have the same value of item_id but be different in the other columns.
The ultimate fix might be to have a group by item_id in the query, instead of select distinct. That would require other changes to the logic. Another possibility would be to use row_number() in a subquery and select the first row.
Related
I didn't find a working solution for creating a "lookup column" in a Firebird database.
Here is an example:
Table1: Orders
[OrderID] [CustomerID] [CustomerName]
Table2: Customers
[ID] [Name]
When I run SELECT * FROM ORDERS I want to get OrderID, CustomerID and CustomerName....but CustomerName should automatically be computed by looking for the "CustomerID" in the "ID" column of "Customer" Table, returning the content of the "Name" column.
Firebird has calculated fields (generated always as/computed by), and these allow selecting from other tables (contrary to an earlier version of this answer, which stated that Firebird doesn't support this).
However, I suggest you use a view instead, as I think it performs better (haven't verified this, so I suggest you test this if performance is important).
Use a view
The common way would be to define a base table and an accompanying view that gathers the necessary data at query time. Instead of using the base table, people would query from the view.
create view order_with_customer
as
select orders.id, orders.customer_id, customer.name
from orders
inner join customer on customer.id = orders.customer_id;
Or you could just skip the view and use above join in your own queries.
Alternative: calculated fields
I label this as an alternative and not the main solution, as I think using a view would be the preferable solution.
To use calculated fields, you can use the following syntax (note the double parentheses around the query):
create table orders (
id integer generated by default as identity primary key,
customer_id integer not null references customer(id),
customer_name generated always as ((select name from customer where id = customer_id))
)
Updates to the customer table will be automatically reflected in the orders table.
As far as I'm aware, the performance of this option is less than when using a join (as used in the view example), but you might want to test that for yourself.
FB3+ with function
With Firebird 3, you can also create calculated fields using a trigger, this makes the expression itself shorter.
To do this, create a function that selects from the customer table:
create function lookup_customer_name(customer_id integer)
returns varchar(50)
as
begin
return (select name from customer where id = :customer_id);
end
And then create the table as:
create table orders (
id integer generated by default as identity primary key,
customer_id integer not null references customer(id),
customer_name generated always as (lookup_customer_name(customer_id))
);
Updates to the customer table will be automatically reflected in the orders table. This solution can be relatively slow when selecting a lot of records, as the function will be executed for each row individually, which is a lot less efficient than performing a join.
Alternative: use a trigger
However if you want to update the table at insert (or update) time with information from another table, you could use a trigger.
I'll be using Firebird 3 for my answer, but it should translate - with some minor differences - to earlier versions as well.
So assuming a table customer:
create table customer (
id integer generated by default as identity primary key,
name varchar(50) not null
);
with sample data:
insert into customer(name) values ('name1');
insert into customer(name) values ('name2');
And a table orders:
create table orders (
id integer generated by default as identity primary key,
customer_id integer not null references customer(id),
customer_name varchar(50) not null
)
You then define a trigger:
create trigger orders_bi_bu
active before insert or update
on orders
as
begin
new.customer_name = (select name from customer where id = new.customer_id);
end
Now when we use:
insert into orders(customer_id) values (1);
the result is:
id customer_id customer_name
1 1 name1
Update:
update orders set customer_id = 2 where id = 1;
Result:
id customer_id customer_name
1 2 name2
The downside of a trigger is that updating the name in the customer table will not automatically be reflected in the orders table. You would need to keep track of these dependencies yourself, and create an after update trigger on customer that updates the dependent records, which can lead to update/lock conflicts.
No need here a complex lookup field.
No need to add a persistant Field [CustomerName] on Table1.
As Gordon said, a simple Join is enough :
Select T1.OrderID, T2.ID, T2.Name
From Customers T2
Join Orders T1 On T1.IDOrder = T2.ID
That said, if you want to use lookup Fields (as we do it on a Dataset) with SQL you can use some thing like :
Select T1.OrderID, T2.ID,
( Select T3.YourLookupField From T3 where (T3.ID = T2.ID) )
From Customers T2 Join Orders T1 On T1.IDOrder = T2.ID
Regards.
It runs but I select all the columns. Can someone explain to me why my first query doesn't work? I don't think I need a join. If I can get some help that would be good. To be quite honest I've never seen the error before. If it works with SELECT*, I don't understand why I have issues with select specific columns.
These are my tables:
create table product
(
pdt# varchar(10) not null,
pdt_name varchar(30) not null,
pdt_label varchar(30) not null,
constraint product_pk primary key (pdt#));
create table orders
(
pdt# varchar(10) not null,
qty number(11,0) not null,
city varchar(30) not null
);
And these are the values
insert into product values ([111,chair,chr]);
insert into product values ([222,stool,stl]);
insert into product values ([333,table,tbl]);
insert into orders values ([111,22,Ottawa]);
insert into orders values ([222,22,Ottawa]);
insert into orders values ([333,22,Toronto]);
Question is this:
c. List all [pdt#,pdt_name,qty] when the order is from [Ottawa]
I tried:
SELECT pdt#, pdt_name, qty FROM orders, product WHERE city='Ottawa';
I get column is ambiguously defined error. But when I run:
SELECT *, qty FROM orders, product WHERE city='Ottawa';
It runs but I select all the columns. Can someone explain to me why my first query doesn't work? I don't think I need a join. If I can get some help that would be good. To be quite honest I've never seen the error before. If it works with SELECT*, I don't understand why I have issues with select specific columns.
This is because both the tables have pdt# in common and you are selecting it in your query. In cases like these, you have to explicitly specify the table from which the column should be picked up.
You should also join the tables. Else you would get a cross-joined result.
SELECT p.pdt#, p.pdt_name, o.qty
FROM orders o join product p on o.pdt# = p.pdt#
WHERE o.city='Ottawa';
Your second query works because you are selecting all the columns from both the tables and ideally it should not be done. Always specify the columns you need when you are selecting from more than one table.
I have two tables, a promotion table and a prize table.
CREATE TABLE PRIZE(
PRIZEID INT NOT NULL PRIMARY KEY,
COST DOUBLE NOT NULL,
PRIZENAME VARCHAR(100) NOT NULL,
)
CREATE TABLE PROMOTION (
PROMOTIONID INTEGER NOT NULL,
LEVEL INTEGER NOT NULL,
AMOUNT NOT NULL,
COST DOUBLE NOT NULL DEFAULT 0,
PRIZENAME VARCHAR(100) NOT NULL DEFAULT ' ',
PRIZEID INTEGER
)
The prize table is currently empty and I want to copy records from the promotion table into the prize table. in doing this I only want to select those records that have unique values in two columns, the prizename and the cost. I will be dropping those columns from promotion afterwards.
Right now I have the following sql statement
INSERT INTO prize(PRIZEID, COST, PRIZENAME)
SELECT r.PRIZEID, r.COST, r.PRIZENAME
FROM PROMOTION r;
but this will insert all records into the prize table. I realize I can use the distinct keyword in the select to select unique instances of cost and prizename but in my case the prizeid will always be unique and since the distinct keyword applies to all columns in the select clause it won't help.
Thanks in advance!
You'll have to just replace the PRIZEID value with new ones. Because it sounds like you currently have duplicates on your PROMOTION table
First add all the distinct PRIZENAMEs and COSTs to your new PRIZE table:
INSERT INTO prize(PRIZEID, COST, PRIZENAME)
SELECT DISTINCT (SELECT MAX(PRIZEID)+1 FROM PRIZE), r.COST, r.PRIZENAME
FROM PROMOTION r;
Then update your PROMOTIONs table with the new PRIZEID
UPDATE PROMOTION R
SET R.PRIZEID =
(SELECT P.PRIZEID
FROM PRIZE
WHERE P.PRIZENAME=R.PRIZENAME
AND P.COST=R.COST);
Then, I think from there you can safely delete the columns from your PROMOTIONs table
This will get the unique prizes based on prizename and cost and get the lowest prizeid for the group.
INSERT INTO prize(PRIZEID, COST, PRIZENAME)
SELECT MIN(r.PRIZEID), r.COST, r.PRIZENAME
FROM PROMOTION r
GROUP BY r.COST, r.PRIZENAME
;
I have a table with a certain number of columns and a primary key column (suppose OriginalKey). I perform a GROUP BY on a certain sub-set of those columns and store them in a temporary table with primary key (suppose GroupKey). At a later stage, I may need to get more details about one or more of those groupings (which can be found in the temporary table) i.e. I need to know which were the rows from the original table that formed that group. Simply put, I need to know the mappings between GroupKey and OriginalKey. What's the best way to do this? Thanks in advance.
Example:
Table Student(
StudentID INT PRIMARY KEY,
Level INT, --Grade/Class/Level depending on which country you are from)
HomeTown TEXT,
Gender CHAR)
INSERT INTO TempTable SELECT HomeTown, Gender, COUNT(*) AS NumStudents FROM Student GROUP BY HomeTown, Gender
On a later date, I would like to find out details about all towns that have more than 50 male students and know details of every one of them.
How about joining the 2 tables using the GroupKey, which, you say, are the same?
Or how about doing:
select * from OriginalTable where
GroupKey in (select GroupKey from my_temp_table)
You'd need to store the fields you grouped on in your temporary table, so you can join back to the original table. e.g. if you grouped on fieldA, fieldB, and fieldC, you'd need something like:
select original.id
from original
inner join temptable on
temptable.fieldA = original.fieldA and
temptable.fieldB = original.fieldB and
temptable.fieldC = original.fieldC
This is my Insert Statement
INSERT INTO ProductStore (ProductID, StoreID, CreatedOn)
(SELECT DISTINCT(ProductId), 1, GETDATE() FROM ProductCategory
WHERE EXISTS (SELECT StoreID, EntityID FROM EntityStore
WHERE EntityType = 'Category' AND ProductCategory.CategoryID = EntityStore.EntityID AND StoreID = 1))
I am trying to Insert into table ProductStore, all the Products Which are mapped to Categories that are mapped to Store 1. Column StoreID can definitely have more than one row with the same entry. And I am getting the following error: Violation of Primary Key Constraint...
However, the Following query does work:
INSERT INTO ProductStore (ProductID, StoreID, CreatedOn)
VALUES (2293,1,GETDATE()),(2294,1,GETDATE())
So apparently, the ProductID Column is trying to insert the same one more than once.
Can you see anything wrong with my query?
TIA
I don't see any part of that query that excludes records already in the table.
Take out the INSERT INTO statement and just run the SELECT - you should be able to spot pretty quickly where the duplicates are.
My guess is that you're slightly mistaken about what SELECT DISTINCT actually does, as evidenced by the fact that you have parentheses around the ProductId. SELECT DISTINCT only guarantees the elimination of duplicates when all columns in the select list are the same. It won't guarantee in this case that you only get one row for each ProductId.
select distinct productid is selecting an existing ID and therefor in violation with your primary key constraint.
Why don't you create the primary key using Identity increment? In that case you don't need to worry about the ID itself, it will be generated for you.