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SELECT
first_name || ' ' || last_name full_name,
SUM (amount) amount
FROM
payment
INNER JOIN customer USING (customer_id)
GROUP BY
full_name
ORDER BY amount;
Can i know how does this query works for group by full_name, by rigth the query should give error because of the order of the sql execution(https://stackoverflow.com/a/3841804/15279872). The output of the above query can be seen in this link (https://www.postgresqltutorial.com/postgresql-group-by/) under the Section 3 : Using PostgreSQL GROUP BY clause with the JOIN clause
Here is what the documentation says about GROUP BY in PostgreSQL:
In the SQL-92 standard, an ORDER BY clause can only use output column
names or numbers, while a GROUP BY clause can only use expressions
based on input column names. PostgreSQL extends each of these clauses
to allow the other choice as well (but it uses the standard's
interpretation if there is ambiguity). PostgreSQL also allows both
clauses to specify arbitrary expressions. Note that names appearing in
an expression will always be taken as input-column names, not as
output-column names.
SQL:1999 and later use a slightly different definition which is not
entirely upward compatible with SQL-92. In most cases, however,
PostgreSQL will interpret an ORDER BY or GROUP BY expression the same
way SQL:1999 does.
The “output column name” mentioned above can be an alias, so PostgreSQL allows aliases in the GROUP BY clause.
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I need to execute a query with WITH statement. If I run it, my WITH data shows error. This is my sample query please guide me to execute it.
with
x1_fields as
(SELECT
x1.id as x_id,
x1.created_time as x_created,
sum(x1.value) as x_sum
FROM
xxxx1 x1
INNER JOIN xxxx2 x2 ON x2.id = x1.id
INNER JOIN xxxx3 x3 ON x3.id = x2.id
WHERE
x1.customer = 'microsoft'
GROUP BY
x1.id,
x1.created_time
)
SELECT
y.id as final_id,
x_t.sum as final_sum
FROM
yyyy as y
left join x1_fields as x_t on x_t.x_id = y.id
where
y.customer = 'microsoft'
and y.id = '123456'
I have try to run this query in DBeaver but I can't run this. But it works in SSRS. I need to check such queries in some SQL software and debug it. Please give me some instructions to solve this.
Since we don't know your database and table structure, we cannot find an error which might occure because of wrong relation names or something.
However: Syntax error is the , character after the WITH clause (before the final SELECT). You have to remove it.
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I have a large set of records in my database. I tried to run SQL query using where condition. I got the data and I show count of records also. It taking around 21 secs. I need to reduce the time.
Sql Query
select * from sample_rank where company_id = 1
Records Count
166270266
I added Index in db. but It's not fastly getting data. How to fix it and How to change the query
Assuming, going by your comments, that you only need to select two of the columns in your table:
SELECT col1, col2 FROM sample_rank WHERE company_id = 1;
then the following covering index is probably the best you can do here:
CREATE INDEX idx ON sample_rank (company_id, col1, col2);
The above index completely covers the entire query, meaning that, if used, your SQL engine can use the index alone to satisfy the entire query plan. I put "if" in bold, because depending on the cardinality of the data, the above index might not help the query run faster. For example, if you only have two company_id values, 1 and 2, with 50% of the record having each value, then your SQL engine might just decide that a full table scan would be faster than even resorting to use the index. As suggested in the comments, running EXPLAIN on your actual query would reveal more information.
Can anyone please help me in writing a single query joining these two queries.
I am using IBM DB2.
(SELECT
TABLE1.COLS,TBLE2.COLS,TABLE3.COLS
FROM
TABLE1,TABLE2,TABLE3,TABLE_PROB
WHERE
TABLE_PROB.COL=TABLE1.COL,OTHER_CLAUSE )
UNION
(SELECT
TABLE1.COLS,TBLE2.COLS,TABLE3.COLS
FROM
TABLE1,TABLE2,TABLE3,TABLE_PROB1
WHERE TABLE_PROB1.COL=TABLE1.COL,OTHER_CLAUSE )
The two queries before and after union are same except that instead of "TABLE_PROB" it is changed to "TABLE_PROB1". There are no columns is to be selected from both the tables, they are only used to filter in the where clause.
Can anyone tell me how to combine both into a single query.
This query can be considered for the following scenario.
There are few employee details table which contains details of all employees.
"TABLE_PROB" contains list of contract employees and "TABLE_PROB1" contains list of permanent employees. I need to get the details of both the contract and not contract employees based on few criteria.
Since the query has big Whereclause and select clause firing two queries by using union,increases the cost of the query. So I need to merge it by making a single query.
Thanks for the help in advance.
You cannot avoid the UNION because you still have to access both TABLE_PROB and TABLE_PROB1. Depending on your DB2 version, platform, and the system configuration this might perform a bit better:
SELECT
TABLE1.COLS,TBLE2.COLS,TABLE3.COLS
FROM
TABLE1,TABLE2,TABLE3
WHERE
OTHER_CLAUSE
AND
EXISTS (
SELECT 1
FROM TABLE_PROB
WHERE COL=TABLE1.COL
UNION
SELECT 1
FROM TABLE_PROB1
WHERE COL=TABLE1.COL
)
Depending on the contents of TABLE_PROB.COL and TABLE_PROB1.COL UNION ALL instead of UNION might also prove beneficial.
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I am new to PostgreSQL and I am learning by taking few examples!
I am solving a queries in PostgreSQL and I came with few but got stuck at one point!
Given the sample data in the SQLFiddle below, I tried:
--6.find most sold product with with sales_id, product_name,quantity and sum(price)
select array_agg(s.sale_id),p.product_name,s.quantity,sum(s.price)
from products p
join sales s
on p.product_id=s.product_id;
but it fails with:
ERROR: column "p.product_name" must appear in the GROUP BY clause or be used in an aggregate function:
This is the SQL Fiddle with sample data.
I'm using PostgreSQL 9.2.
For all that it looks simple, this is quite an interesting problem.
The unsolved #6
There are two stages to this:
find the most sold product; and
display the required detail on that product
The question is badly written; it fails to specify whether you want
the product with the greatest number of sales, or the greatest
dollar sales value. I will assume the former, but it's easy to adapt the following queries to sort by total price instead.
UPDATE: #user2561626 found the simple solution I mentioned I was sure I was overlooking but couldn't think of: http://sqlfiddle.com/#!12/dbe7c/118 . Use the output of SUM in ORDER BY then LIMIT the result set.
The following are the complicated and roundabout ways I tried because I couldn't think of the simple way:
One way is to use a subquery with an ORDER BY and LIMIT to sort products by total number of sales, then pick the top one. You then join on that inner query to generate the desired product summary. In this case I join on sales twice, once in the inner query and once in the outer where I calculate more detail for just one product. It's possibly more efficient to join on it just once in the inner query and do more work, but that'll involve creating and discarding a bigger result set, so it's the sort of thing you'd tune based on your data distribution.
SELECT
array_agg(s.sale_id) AS sales_ids,
(SELECT p.product_name FROM products p WHERE p.product_id = pp.product_id) AS product_name,
sum(s.quantity) AS total_quantity,
sum(s.price) AS total_price
FROM
(
-- Find the product with the largest number of sales
-- If multiple products have the same sales an arbitrary candidate
-- is selected; extend the ORDER BY if you want to control which
-- one gets picked.
SELECT
s2.product_id, sum(s2.quantity) AS total_quantity
FROM sales s2
GROUP BY s2.product_id
ORDER BY 2 DESC
LIMIT 1
) AS pp
INNER JOIN sales s ON (pp.product_id = s.product_id)
GROUP BY s.product_id, pp.product_id;
I'm honestly not too sure how to phrase this in purely standard SQL (i.e. no LIMIT clause). You can use a CTE or multiple scans in subqueries to find the greatest number of sales and the product Id with the greatest number of sales, but that'll give you multiple results if you have more than one product with equal sales.
I can't help but feel I've totally forgotten the simple and obvious way to do this.
Comments on others:
--1.write the query find the products which are not soled
select *
from products
where product_id not in (select distinct PRODUCT_ID from sales );
Your solution is subtly incorrect, because there's no NOT NULL constraint on product_id in sales. It builds a list then filters on the list, but the list could contain NULL, and 2 NOT IN (1, NULL) is NULL, which in WHERE is treated as false.
It is much better to re-phrase this as WHERE NOT EXISTS (SELECT 1 FROM sales s WHERE s.product_id = products.product_id).
With #2 it's again better to use EXISTS, but PostgreSQL can optimize it into the better form automatically since it's semantically the same; the NULL issue doesn't apply for IN, only NOT IN. So your query is fine.
Question #7 highlights that this is an awful schema. You should never store split-up year/month/day like this; a sale would just have a single timestamptz field, and to get the year you'd use date_trunc or extract. That's not your fault, it's bad table design in the question. The question could also be clearer; I think you've answered it correctly as written, but they don't say whether or not years with no sales should be shown - presumably they assume there aren't any. If there are, you'd have to do a left outer join over a generate_series of dates to zero-fill empty years.
Question #8 is another bad question, frankly. "max price". Um. What? "Maximum price paid per item" would be "price/quantity". "Greatest total individual sale value for each product" would be what you wrote. The question seems to allow for either.
The Query Solution for Question#6 is ::
select array_agg(s.sale_id),p.product_name,sum(s.quantity) as Quantity ,sum(s.price) as Total_Price
from sales s,products p
where s.product_id =p.product_id
group by p.product_id
order by sum(s.quantity) desc limit 1 ;
Comment On Others
Question#9: #Robin Hood's
select s.sale_id,p.product_name,s.quantity,s.price
from products p,sales s
where p.product_id=s.product_id and p.product_name LIKE 'S%';
the 'S%' is a case Sensitive .. so it how it works..
Question#10: #Robin Hood's
Stored Procedure is:
CREATE OR REPLACE FUNCTION get_details()
RETURNS TABLE(sale_id integer,product_name varchar,quantity integer,price int) AS
$BODY$
BEGIN
RETURN QUERY
select s.sale_id,p.product_name,s.quantity,s.price
from products p
join sales s
on p.product_id =s.product_id ;
Exception WHEN no_data_found then
RAISE NOTICE 'No data available';
END
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
select * from get_details(); then you will get the result.
I need a help over these questions even !! i just want to add these queries to.
--Question#9
--9. select product details with sales_id, product_name,quantity and price those product names are started with letter ‘s’
--This selects my product details
select s.sale_id,p.product_name,s.quantity,s.price
from products p,sales s
where p.product_id=s.product_id ;
--This is'nt working to find those names which start with s.. is there any other way to solve this..
select s.sale_id,p.product_name,s.quantity,s.price
from products p,sales s
where p.product_id=s.product_id and product_name = 's%';
--10. write the stored procedure for extract all the sales and product details with sales_id, product_name,quantity and price with exception handling and raisint the notices
I have created a database as part of university assignment and I have hit a snag with the question in the title.
More likely I am being asked to find out how many films each company has made. Which suggests to me a group by query. But I have no idea where to begin. It is only a two mark question but the syntax is not clicking in my head.
My schema is:
CREATE TABLE Movie
(movieID CHAR(3) ,
title CHAR(36),
year NUMBER,
company CHAR(50),
totalNoms NUMBER,
awardsWon NUMBER,
DVDPrice NUMBER(5,2),
discountPrice NUMBER(5,2))
There are other tables but at first glance I don't think they are relevant to this question.
I am using sqlplus10
The answer you need comes from three basic SQL concepts, I'll step through them with you. If you need more assistance to create an answer from these hints, let me know and I can try to keep guiding you.
Group By
As you mentioned, SQL offers a GROUP BY function that can help you.
A SQL Query utilizing GROUP BY would look like the following.
SELECT list, fields, aggregate(value)
FROM tablename
--WHERE goes here, if you need to restrict your result set
GROUP BY list, fields
a GROUP BY query can only return fields listed in the group by statement, or aggregate functions acting on each group.
Aggregate Functions
Your homework question also needs an Aggregate function called Count. This is used to count the results returned. A simple query like the following returns the count of all records returned.
SELECT Count(*)
FROM tablename
The two can be combined, allowing you to get the Count of each group in the following way.
SELECT list, fields, count(*)
FROM tablename
GROUP BY list, fields
Column Aliases
Another answer also tried to introduce you to SQL column aliases, but they did not use SQLPLUS syntax.
SELECT Count(*) as count
...
SQLPLUS column alias syntax is shown below.
SELECT Count(*) "count"
...
I'm not going to provide you the SQL, but instead a way to think about it.
What you want to do is select where the company matches and count the total rows returned. That count is the number of films made by the specified company.
Hope that points you in the right direction.
Select company, count(*) AS count
from Movie
group by company
select * group by company won't work in Oracle.