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.
Related
I am learning SQL (postgres) and am trying to insert a record into a table that references records from two other tables, as foreign keys.
Below is the syntax I am using for creating the tables and records:
-- Create a person table + insert single row
CREATE TABLE person (
pname VARCHAR(255) NOT NULL,
PRIMARY KEY (pname)
);
INSERT INTO person VALUES ('personOne');
-- Create a city table + insert single row
CREATE TABLE city (
cname VARCHAR(255) NOT NULL,
PRIMARY KEY (cname)
);
INSERT INTO city VALUES ('cityOne');
-- Create a employee table w/ForeignKey reference
CREATE TABLE employee (
ename VARCHAR(255) REFERENCES person(pname) NOT NULL,
ecity VARCHAR(255) REFERENCES city(cname) NOT NULL,
PRIMARY KEY(ename, ecity)
);
-- create employee entry referencing existing records
INSERT INTO employee VALUES(
SELECT pname FROM person
WHERE pname='personOne' AND <-- ISSUE
SELECT cname FROM city
WHERE cname='cityOne
);
Notice in the last block of code, where I'm doing an INSERT into the employee table, I don't know how to string together multiple SELECT sub-queries to get both the existing records from the person and city table such that I can create a new employee entry with attributes as such:
ename='personOne'
ecity='cityOne'
The textbook I have for class doesn't dive into sub-queries like this and I can't find any examples similar enough to mine such that I can understand how to adapt them for this use case.
Insight will be much appreciated.
There doesn’t appear to be any obvious relationship between city and person which will make your life hard
The general pattern for turning a select that has two base tables giving info, into an insert is:
INSERT INTO table(column,list,here)
SELECT column,list,here
FROM
a
JOIN b ON a.x = b.y
In your case there isn’t really anything to join on because your one-column tables have no column in common. Provide eg a cityname in Person (because it seems more likely that one city has many person) then you can do
INSERT INTO employee(personname,cityname)
SELECT p.pname, c.cname
FROM
person p
JOIN city c ON p.cityname = c.cname
But even then, the tables are related between themselves and don’t need the third table so it’s perhaps something of an academic exercise only, not something you’d do in the real world
If you just want to mix every person with every city you can do:
INSERT INTO employee(personname,cityname)
SELECT pname, cname
FROM
person p
CROSS JOIN city c
But be warned, two people and two cities will cause 4 rows to be inserted, and so on (20 people and 40 cities, 800 rows. Fairly useless imho)
However, I trust that the general pattern shown first will suffice for your learning; write a SELECT that shows the data you want to insert, then simply write INSERT INTO table(columns) above it. The number of columns inserted to must match the number of columns selected. Don’t forget that you can select fixed values if no column from the query has the info (INSERT INTO X(p,c,age) SELECT personname, cityname, 23 FROM ...)
The following will work for you:
INSERT INTO employee
SELECT pname, cname FROM person, city
WHERE pname='personOne' AND cname='cityOne';
This is a cross join producing a cartesian product of the two tables (since there is nothing to link the two). It reads slightly oddly, given that you could just as easily have inserted the values directly. But I assume this is because it is a learning exercise.
Please note that there is a typo in your create employee. You are missing a comma before the primary key.
When using a single insert statement to add multiple records into a table as shown below, it does not follow the same order when selecting. I understand that it does not affect anything but may I know why is this the case?
CREATE TABLE [category]
(
[category_id] int IDENTITY(1,1) PRIMARY KEY,
[category_name] varchar(255) NOT NULL UNIQUE
);
INSERT INTO [category] (category_name)
VALUES ('Laptops and Accessories'),
('AI Development Kit'),
('Cameras and Lens');
SELECT * FROM [category]
Output:
I'm using SQL Server.
Your select statement explicitly says: "I do not care about the order!" - it does so by omitting the ORDER BY clause.
If you say SELECT * FROM [category] ORDER BY [category_id] you will get an ordered result set along the lines of
1, 'Laptops and Accessories'
2, 'AI Development Kit'
3, 'Cameras and Lens'
Which is exatly the order you gave in your INSERT statement.
SELECTs in SQL without an ORDER BY clause are not only not expected to be in some order, they are also not expected to have the same order when called multiple times.
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.
I need to collect the values from the column "EmployeeID" of the table "Employees" and insert them into the column "EmployeeID" of the table "Incident".
At the end, the Values in the rows of the column "EmployeeID" should be arranged randomly.
More precisely;
I created 10 employees with their ID's, counting from 1 up to 10.
Those Employees, in fact the ID's, should receive random Incidents to work on.
So ... there are 10 ID's to spread on all Incidents - which might be 1000s.
How do i do this?
It's just for personal exercise on the local maschine.
I googled, but didn't find an explicit answer to my problem.
Should be simple to solve for you champs. :)
May anyone help me, please?
NOTES:
1) I've already created a column called "EmployeeID" in the table "Incident", therefore I'll need an update statement, won't I?
2) Schema:
[dbo].[EmployeeType]
[dbo].[Company]
[dbo].[Division]
[dbo].[Team]
[dbo].[sysdiagrams]
[dbo].[Incident]
[dbo].[Employees]
3) 1. Pre-solution:
CREATE TABLE IncidentToEmployee
(
IncidentToEmployeeID BIGINT IDENTITY(1,1) NOT NULL,
EmployeeID BIGINT NULL,
Incident FLOAT NULL
PRIMARY KEY CLUSTERED (IncidentToEmployeeID)
)
INSERT INTO IncidentToEmployee
SELECT
EmployeeID,
Incident
FROM dbo.Employees,
dbo.Incident
ORDER BY NEWID()
SELECT * FROM IncidentToEmployee
GO
3) 2. Output by INNER JOIN ON
In case you are wondering about the "Alias" column;
Nobody really knows which persons are behind the ID's - that's why I used an Alias column.
SELECT Employees.Alias,
IncidentToEmployee.Incident
FROM Employees
INNER JOIN
IncidentToEmployee ON
Employees.EmployeeID = IncidentToEmployee.EmployeeID
ORDER BY Alias
4) Final Solution
As I mentioned, I added at first a column called "EmployeeID" already to my "Incident" table. That's why I couldn't use an INSERT INTO statement at first and had to use an UPDATE statement. I found the most suitable solution now - without creating a new table as I did as a pre-solution.
Take a look at the following code:
ALTER Table Incident
ADD EmployeeID BIGINT NULL
UPDATE Incident
SET Incident.EmployeeID = EmployeeID
FROM Incident INNER JOIN Employees
ON Incident = EmployeeID
SELECT
EmployeeID,
Incident
FROM dbo.Employees,
dbo.Incident
ORDER BY NEWID()
Thank you all for your help - It took way longer to find a solution as I thought it would take; but I finally made it. Thanks!
UPDATE
I think you need to allocate different task to different user, a better approach will be to create a new table let's say EmployeeIncidents having columns Id(primary) , EmployeeID and IncidentID .
Now you can insert random EmployeesID and random IncidentID to new table, this way you will be able to keep records also ,
Updating Incident table will not be a smart choice.
INSERT INTO EmployeeIncidents
SELECT TOP ( 10 )
EmployeesID ,
IncidentID
FROM dbo.Employees,
dbo.Incident
ORDER BY NEWID()
Written by hand, so may need to tweak syntax, but something like this should do it. The Rand() function will give the same value unless seeded, so you can see with something like date to get randomness.
Insert Into Incidents
Select Top 10
EmployeeID
From Employees
Order By
Rand(GetDate())
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.