QUESTION: I need to develop a query that looks for certain records that starts with a search term and records that contains the search term. Furthermore, both subsets should be sorted by a certain column, whereas the resultant set shouldn't be sorted. Records starting with term should come above the contains term records.
Example: I have students table and I want all students whose names start with "Jhon". Students having the first name "Jhon" should come first and after then all those students whose last name is "Jhon".
What I have are as following:
Got all records starting with the search term and save it into a temptable_A , than got all records all records containing the search term and excluding results that are already in temptable_A and save into temptable_B. Now both temptable should have respected results, so I dump tempTable_B into tempTable_A, believing that the new records are append at last of the table. But they are not, they are inserted in and are sorted, where are I haven't applied sorting.
I have done the same with a merge statement and it does the same thing, but no fruitful result.
I have tried Union between both sub queries (Start with and contains) but the resultant dataset always doesn't show the start with records on top.
Scenario:
Students Table with column
Id | Student
select * FROM students where name like 'jhon%'
UNION
select * FROM students where name like '%jhon%'
Use an order by. For instance:
select s.*
from students
where name like '%jhon%'
order by charindex('jhon', name);
This orders by how far down 'jhon' is in the string. If you just want the ones that start 'jhon' first, you can use a case expression:
order by (case when name like 'jhon%' then 1 else 2 end)
You can do this with a case expression in the ORDER BY clause:
select * from students where Name like '%jhon%' -- select all students containing john
order by
case -- order by place of match first
when Name like 'john%' then 0
when Name like '%john%' then 1
end,
Name -- then order by Name
Related
I just started learning SQL and am trying to learn from my mistakes. In one of my practice exercises, I had to find city names from the cities database are not listed as capital cities in countries database. Initially I tried the code below but it yielded an error.
SELECT name
FROM cities
EXCEPT
SELECT capital
FROM countries
ORDER BY capital ASC;
The correct code is:
SELECT city.name
FROM cities AS city
EXCEPT
SELECT country.capital
FROM countries AS country
ORDER BY name;
Can someone explain to me why aliasing made all the difference here?
An ORDER BY for a UNION, EXCEPT or INTERSECT sorts the complete result. The column names of the overall query are defined by the first query. So this query:
SELECT name
FROM cities
EXCEPT
SELECT capital
FROM countries
returns a result with a single column named name.
Adding an order by is conceptually the same as:
select *
from (
SELECT name
FROM cities
EXCEPT
SELECT capital
FROM countries
) x
order by ....;
As the inner query only returns a single column name, that's the only column you can use in the order by.
The aliases that you used in your second query don't change the column name of the overall result which determines the column names available for the order by clause.
I shall link my database down below.
I have a query called 'TestMonday1' and what this does is return the student with the fewest 'NoOfFrees' and insert the result of the query into the lesson table. Running the query should help explain what i mean. The problem im having is my SQL code has 'SELECT TOP 1' yet if the query returns two students who have the same number of frees it returns both these records. Wit this being a timetable planner, it should only ever return one result, i shall also put the code below,
Many thanks
Code:
INSERT INTO Lesson ( StudentID, LessonStart, LessonEnd, DayOfWeek )
SELECT TOP 1 Availability.StudentID, Availability.StartTime,
Availability.EndTime, Availability.DayOfWeek
FROM Availability
WHERE
Availability.StartTime='16:00:00' AND
Availability.EndTime='18:00:00' AND
Availability.DayOfWeek='Monday' AND
LessonTaken IS NULL
ORDER BY
Availability.NoOfFrees;
This happens because Access returns all records in case of ties in ORDER BY (all records returned have the same values of fields used in ORDER BY).
You can add another field to ORDER BY to make sure there's no ties. StudentID looks like a good candidate (though I don't know your schema, replace with something else if it suits better):
ORDER BY
Availability.NoOfFrees, Availability.StudentID;
Say I have a student table with the following fields - student id, student name, age, gender, marks, class.Assume that due to some error, there are multiple entries corresponding to each student. My requirement is to identify the duplicate rows in the table and the filter criterion is the student name and the class.But in the query result, in addition to identifying the duplicate records, I also need to find the original student detail which got duplicated. Is there any method to do this. I went through this answer: SQL: How to find duplicates based on two fields?. But here it only specifies how to find the duplicate rows and not a means to identify the actual row that was duplicated. Kindly throw some light on the possible solution. Thanks.
First of all: if the columns you've listed are all in the same table, it looks like your database structure could use some normalization.
In terms of your question: I'm assuming your StudentID field is a database generated, primary key and so has not been duplicated. (If this is not the case, I think you have bigger problems than just duplicates).
I'm also assuming the duplicate row has a higher value for StudentID than the original row.
I think the following should work (Note: I haven't created a table to verify this so it might not be perfect straight away. If it doesn't it should be fairly close)
select dup.StudentID as DuplicateStudentID
dup.StudentName, dup.Age, dup.Gender, dup.Marks, dup.Class,
orig.StudentID as OriginalStudentId
from StudentTable dup
inner join (
-- Find first student record for each unique combination
select Min(StudentId) as StudentID, StudentName, Age, Gender, Marks, Class
from StudentTable t
group by StudentName, Age, Gender, Marks, Class
) orig on dup.StudentName = orig.StudenName
and dup.Age = orig.Age
and dup.Gender = orig.Gender
and dup.Marks = orig.Marks
and dup.Class = orig.Class
and dup.StudentID > orig.StudentID -- Don't identify the original record as a duplicate
I need the second column of the table retrieved from a query to have a count of the number of rows, so row one would have a 1, row 2 would have a 2 and so on. I am not very proficient with sql so I am sorry if this is a simple task.
A basic example of what I am doing would be is:
SELECT [Name], [I_NEED_ROW_COUNT_HERE],[Age],[Gender]
FROM [customer]
The row count must be the second column and will act as an ID for each row. It must be the second row as the text file it is generating will be sent to the state and they require a specific format.
Thanks for any help.
With your edit, I see that you want a row ID (normally called row number rather than "count") which is best gathered from a unique ID in the database (person_id or some other unique field). If that isn't possible, you can make one for this report with ROW_NUMBER() OVER (ORDER BY EMPLOYEE_ID DESC) AS ID, in your select statement.
select Name, ROW_NUMBER() OVER (ORDER BY Name DESC) AS ID,
Age, Gender
from customer
This function adds a field to the output called ID (see my tips at the bottom to describe aliases). Since this isn't in the database, it needs a method to determine how it will increment. After the over keyword it orders by Name in descending order.
Information on Counting follows (won't be unique by row):
If each customer has multiple entries but the selected fields are the same for that user and you are counting that user's records (summed in one result record for the user) then you would write:
select Name, count(*), Age, Gender
from customer
group by name, age, gender
This will count (see MSDN) all the user's records as grouped by the name, age and gender (if they match, it's a single record).
However, if you are counting all records so that your whole report has the grand total on every line, then you want:
select Name, (select count(*) from customer) as "count", Age, Gender
from customer
TIP: If you're using something like SSMS to write a query, dragging in columns will put brackets around the columns. This is only necessary if you have spaces in column names, but a DBA will tend to avoid that like the plague. Also, if you need a column header to be something specific, you can use the as keyword like in my first example.
W3Schools has a good tutorial on count()
The COUNT(column_name) function returns
the number of values (NULL values will not be counted) of the
specified column:
SELECT COUNT(column_name) FROM table_name;
The COUNT(*) function returns the number of records in a table:
SELECT COUNT(*) FROM table_name;
The COUNT(DISTINCT column_name) function returns the number of
distinct values of the specified column:
SELECT COUNT(DISTINCT column_name) FROM table_name;
COUNT(DISTINCT) works with ORACLE and Microsoft SQL Server, but
not with Microsoft Access.
It's odd to repeat the same number in every row but it sounds like this is what you're asking for. And note that this might not work in your flavor of SQL. MS Access?
SELECT [Name], (select count(*) from [customer]), [Age], [Gender]
FROM [customer]
I am using SELECT DISTINCT name FROM table to get a table with distinct names that appear in the column. How can i get an extra column returning the number of times that this specific name have appeared on the column?
select name, count(1) from table
group by name;