I'm new to SQL and trying to solve the following problem:
I have rows with the following columns: ID, Sequence, Name
ID can be the same if there are multiple sequences
How can I add the sequences and name and have just one row for each ID with separate columns?
Example : ID 1 Seq 1 Name Blue Seq 2 Name Green Seq 3 Name Red
Hope that makes sense.
you can use the concat option
select id || sequence as id_seq, name from table
the as clause isn't required but can help read-ability
Related
suppose I Have below table
A
B
1
one
2
two
1
three
2
four
1
last
for value in A=1
then I need the output as one;three;last
how can I query this in Oracle's SQL?
If you care whether you get the string "one;three;last" or "three;one;last" or some other combination of the three values, you'd need some additional column to order the results by (a database table is inherently unordered). If there is an id column that you're not showing, for example, that could do that, you'd order by id in the listagg.
If you don't care what order the values appear in the result, you could do something like this
select listagg( b, ';' ) within group (order by a)
from your_table
where a = 1
Suppose, there is a table and I need to sort one of its column (name) alphabetically and at the same time I want to sort it by using ID column in asc order based on the condition ( rows that have same name). So, I failed to understand how this will work. Once the records will be sorted by column (name) then will it sort all rows by using id column?
Can someone explain how actually order by clause works in this case
select name,
id
from hack h
order by name,
id
use order by name, id
select name,
id
from hack
order by name,
id
I just tried to understand what you want to know, you want to realize how it happens when the order by clause have two or more columns ,am I right? Let's go to an example,
the first column is id and the second is name,
2 A
5 B
6 A
3 A
1 B
the result of SQL "select name,id from hack order by name,id" will get the result as below
A 2
A 3
A 6
B 1
B 5
see, it will sort first by name column, and then sort id in the same name value group.
That's it ,did I make it clear?
This answers the original question.
In the code you posted:
substring(name, len(name) - 2, len(name))
returns the last 3 characters of the name.
So you are sorting by these last 3 characters and not by name.
When there are 2 names with the same last 3 characters these will be sorted by id.
If there are more than one column names after "order by" keyword, the system orders the records according to the first column just after order by.
I'm currently trying to select all rows where a certain ID exists within that rows semi-colon delimited ID column.
The Table:
=====================
TOOL_ID | TOOL_USERS
---------------------
1 1;2;3
2 1;3
3 1
=====================
I want to select all the tools that a certain user has access to, for example, the desired result where the user ID is 3:
TOOL_ID | TOOL_USERS
---------------------
1 1;2;3
2 1;3
I know that this design is not normalized, but I do not have the ability to change/modify the database. I could always just query all of the rows and then loop through the results deleting any that don't contain the user id, but I'd rather do this is one nice, clean query.
Is this possible?
Thanks.
You can use the LIKE keyword with wildcards. I included leading and ending semicolons so 13 and stuff doesn't match 3.
SELECT TOOL_ID, TOOL_USERS FROM YourTable WHERE ';' || TOOL_USERS || ';' LIKE '%;3;%'
Someone let me know if I didn't translate this well to PLSQL.
Imagine you've got a table with 2 columns: ID and NAME. ID is simply a number, incrementing for each row (as you'd expect). NAME is some random varchar string. NAME can be same for different rows. Now, imagine you want to get the 3 latest occurences in this table, where NAME only may occur once.
For example, if you've got this data:
ID NAME
1 HELLO
2 TEST
3 HELLO
4 HELLO
5 QWERTY
6 HELLO
Then the result of the question should be:
6 HELLO
5 QWERTY
2 TEST
Is it possible achieve this on SQL level?
SELECT
MAX(ID),
Name
FROM
table
GROUP BY
Name
ORDER BY
MAX(ID) desc
LIMIT 3
SELECT MAX(ID), NAME
FROM THAT_TABLE
GROUP BY NAME
See: GROUP BY (Aggregate) Functions
I suppose, you need to use "DISTINCT" for the "name" column:
SELECT DISTINCT name, id FROM table_name ORDER BY id DESC LIMIT 3;
Another way to achieve this is to use "GROUP BY" for "name" (see another answer)
I have this situation in a certain table:
id | name
1 'Test'
2 'Test'
3 'Test'
How can I make a query to SELECT by distinct the name? I also need the ID column, even if I get the first occurrence of the element, e.g. "if the name column repeats, give me the first record with this repetition."
select name, MIN(ID)
from aCertainTable
group by name