So I have a table that has EMAIL and Order ID.
EMAIL | id
--------------
Y#a.com | 1
Y#a.com | 2
X#a.com | 3
And I need to SELECT it so that I'd have email column that is distinct and ids column that is array of int's
EMAIL | ids
--------------
Y#a.com | [1,2]
X#a.com | [3]
I use PSQL 9.3. I looked at aggregate functions, but since I'm not too good with SQL atm, I didn't really understand them. My code so far is:
SELECT DISTINCT ON (email) email
FROM order
WHERE date > '2013-01-01';
Use the aggregate function array_agg():
SELECT email, array_agg(id) AS id_array
FROM "order"
WHERE date > '2013-01-01'
GROUP BY email;
Aside: your identifiers ...
Don't use order as table name, it's a reserved word.
Don't use date as column name, it's a reserved word in standard SQL and a basic type name in Postgres.
I wouldn't use id as column name either, that's a common anti-pattern, but "id" is not a descriptive name. Once you join a couple of tables you have n columns named "id" and you need to start dealing out column aliases, not to speak of the confusion it may cause.
Instead, use something like this:
CREATE TABLE order_data (
order_data_id serial PRIMARY KEY
, email text
, order_date date
);
Related
I need help with writing this query please ,
in the Database - the customer is registered twice , one row with the email address in the VALUE field and the other row with phone number in the SAME VALUE field .
I want to fetch customer who DO NOT HAVE email address in the VALUE FIELD .
For example , I want to fetch only the last row from the list shown in the figure I shared.
Appreciate your help!
I tried creating multiple SELECT queries , but still not getting the accurate values.
Without seeing table schemas or example data, I'm making an assumption here that you have a field that is common to both rows so you know the customer row with the email value and the customer row with the phone value are linked to the same customer. For the purposes of this example, I'm going to call that field "customer_number".
I'd suggest a query that utilises an auxiliary statement like this:
WITH customers_with_emails AS (
SELECT customer_number
FROM customers
WHERE customer_value LIKE '%#%'
)
SELECT *
FROM customers
WHERE customer_number NOT IN (
SELECT customer_number
FROM customers_with_emails
);
This will return customers with phone numbers, who do not also have an email address.
I suggest that you use the following query, modified with the exact column and table name. We use string_agg to coalesce all the value fields for the same customer id and only show them if none of them contain an # sign.
create table customers(
id int,
name varchar(25),
value varchar(25));
insert into customers values
(1,'Mr A','1234'),
(1,'Mr A','a#b.c'),
(2,'Mr B','6789');
select
id,
max(name) "name",
string_agg(value,', ')
from
customers
group by
id
having
string_agg(value,', ') NOT LIKE '%#%';
id | name | string_agg
-: | :--- | :---------
2 | Mr B | 6789
db<>fiddle here
How can I create a table without knowing in advance how many and what columns it exactly holds?
The idea is that I have a table DATA that has 3 columns : ID, NAME, and VALUE
What I need is a way to get multiple values depending on the value of NAME - I can't do it with simple WHERE or JOIN (because I'll need other values - with other NAME values - later on in my query).
Because of the way this table is constructed I want to PIVOT it in order to transform every distinct value of NAME into a column so it will be easier to get to it in my later search.
What I want now is to somehow save this to a temp table / variable so I can use it later on to join with the result of another query...
So example:
Columns:
CREATE TABLE MainTab
(
id int,
nameMain varchar(max),
notes varchar(max)
);
CREATE TABLE SecondTab
(
id int,
id_mainTab, int,
nameSecond varchar(max),
notes varchar(max)
);
CREATE TABLE DATA
(
id int,
id_second int,
name varchar(max),
value varchar(max)
);
Now some example data from the table DATA:
| id | id_second_int | name | value |
|-------------------------------------------------------|
| 1 | 5550 | number | 111115550 |
| 2 | 6154 | address | 1, First Avenue |
| 3 | 1784 | supervisor | John Smith |
| 4 | 3467 | function | Marketing |
| 5 | 9999 | start_date | 01/01/2000 |
::::
Now imagine that 'name' has A LOT of different values, and in one query I'll need to get a lot of different values depending on the value of 'name'...
That's why I pivot it so that number, address, supervisor, function, start_date, ... become colums.
This I do dynamically because of the amount of possible columns - it would take me a while to write all of them in an 'IN' statement - and I don't want to have to remember to add it manually every time a new 'name' value gets added...
herefore I followed http://sqlhints.com/2014/03/18/dynamic-pivot-in-sql-server/
the thing is know that I want the result of my execute(#query) to get stored in a tempTab / variable. I want to use it later on to join it with mainTab...
It would be nice if I could use #cols (which holds the values of DATA.name) but I can't seem to figure out a way to do this.
ADDITIONALLY:
If I use the not dynamic way (write down all the values manually after 'IN') I still need to create a column called status. Now in this column (so far it's NULL everywhere because that value doesn't exist in my unpivoted table) i want to have 'open' or 'closed', depending on the date (let's say i have start_date and end_date,
CASE end_date
WHEN end_date < GETDATE() THEN pivotTab.status = 'closed'
ELSE pivotTab.status = 'open'
Where can I put this statement? Let's say my main query looks like this:
SELECT * FROM(
(SELECT id_second, name, value, id FROM TABLE_DATA) src
PIVOT (max(value) FOR name IN id, number, address, supervisor, function, start_date, end_date, status) AS pivotTab
JOIN SecondTab ON SecondTab.id = pivotTab.id_second
JOIN MainTab ON MainTab.id = SecondTab.id_mainTab
WHERE pivotTab.status = 'closed';
Well, as far as I can understand - you have some select statement and just need to "dump" its result to some temporary table. In this case you can use select into syntax like:
select .....
into #temp_table
from ....
This will create temporary table according to columns in select statement and populate it with data returned by select datatement.
See MDSN for reference.
I have a table similar to the following:
=> \d table
Table "public.table"
Column | Type | Modifiers
-------------+-----------------------------+-------------------------------
id | integer | not null default nextval( ...
user | bigint | not null
timestamp | timestamp without time zone | not null
field1 | double precision |
As you can see, it contains many field1 values over time for all users. Is there a way to efficiently get the latest field1 value for all users in one query (i.e. one row per user)? I'm thinking I might have to use some combination of group by and select first.
Simplest with DISTINCT ON in Postgres:
SELECT DISTINCT ON (id)
id, timestamp, field1
FROM tbl
ORDER BY id, timestamp DESC;
More details:
https://dba.stackexchange.com/questions/49540/how-do-i-efficiently-get-the-most-recent-corresponding-row/49555#49555
Select first row in each GROUP BY group?
Aside: Don't use timestamp as column name. It's a reserved word in SQL and a basic type name in Postgres.
I've a table like this one:
Column | Type | Modifiers
username | character varying(12) | not null
electioncode | integer | not null
votes | integer | default 0
PRIMARY KEY (username, electioncode)
i need to create a view with username, electioncode, max(votes)
if i use this query it works fine but without username:
SELECT electioncode, max(votes) from table group by electioncode;
if i add username it asks me to add it into the group by but if i do that it gives me the entire table instead of just the username-electioncode-maxvotes
Do you want to get username associated with this number of votes? Or any username in given election code?
If the first:
SELECT
DISTINCT ON ( electioncode )
*
FROM table
ORDER BY electioncode, votes desc;
if the other:
SELECT
electioncode,
min(username),
max(votes)
FROM
table
GROUP BY electioncode;
Your username field seems to be unique. Every record has different username (I am assuming) thus when you group by username it will give you all the records. What you are trying to do has a logic issue not syntax issue.
A suggestion: You want to write on a piece of paper the output you would like to see and then construct the query... If you want Username, Electioncode and max (votes) then imagine how you would display the data where two usernames - user1 and user 2 who have electioncode 001 and voted 1 each? How would you display this?
I have a table like this:
create table t1 {
person_id int,
item_name varchar(30),
item_value varchar(100)
};
Suppose person_id+item_name is the composite key, now I have some data (5 records) in table t1 as below:
person_id ====item_name ====== item_value
1 'NAME' 'john'
1 'GENDER' 'M'
1 'DOB' '1970/02/01'
1 'M_PHONE' '1234567890'
1 'ADDRESS' 'Some Addresses unknown'
Now I want to use SQL (or combing store procedure/function or whatever) to query the above result (1 result set) become:
NAME==GENDER==DOB========M_PHONE=======ADDRESS===============
1 M 1970/02/01 1234567890 Some Addresses unknown
How should I do ?
Thank you for your help.
Regardless of the database you are using, the concept of what you are trying to achieve is called "Pivot Table".
Here's an example for mysql:
http://en.wikibooks.org/wiki/MySQL/Pivot_table
Some databases have builtin features for that, see the links below.
SQLServer:
http://msdn.microsoft.com/de-de/library/ms177410.aspx
Oracle:
http://www.dba-oracle.com/t_pivot_examples.htm
You can always create a pivot by hand. Just select all the aggregations in a result set and then select from that result set. Note, in your case, you can put all the names into one column using concat (i think that's group_concat in mysql), since you cannot know how many names are related to a person_id.
Finally, I found the solution in PostgreSQL:
select * from crosstab ('select person_id, item_name, item_value from t1 where person_id = 1 ')
as virtual_table ( person_id integer, name varchar, gender varchar, dob varchar, m_phone varchar, address varchar)
Also need to install the crosstab function on Postgres. See more: http://www.postgresql.org/docs/8.3/static/tablefunc.html