Question: if this is my data:
col1,col2,col3,col4
===================
www.com,0,dangerous,reason A
www.com,1,dangerous 2,reason B
I want the a single result where column 2 value is max, so I will use in my select the Max(col2) function - but how can I get those corresponding col3 and col4 row ?
select
col1, max(col2), col3, col4
group by
col1
and ???
Thanks
Idan
You can use order by and limit to one row. The ANSI-standard syntax is:
select t.*
from t
order by t.col2 desc
fetch first 1 row only;
Not all databases support the fetch first clause, so you might have to use select top 1, limit, or some other construct.
You can use where in select statement
Like
Select * from table name where col2=max(col2)
You can get max column entire row with single value
If the column col2 which contain same value like 1,1,2,2 at this time above query return the 2 rows. At that time if you want single row you want to use this
Select * from table name where col2=max(col2) fetch first 1 row only
Might be this helpful
Related
How should my SQL be so that the table mentioned above should have the expected output using SQL. The filtering happens using the col 3 value. Row with the highest col 3 value for a particular col 1 value is selected in the output.
You can use ROW_NUMBER() window function
SELECT col1, col2, col3 from (
SELECT row_number() over (partition by col1 order by col3 desc) sn, * from your_table_name
) a WHERE sn=1;
I assume you require the usage of the WHERE clause in SQL which acts as a method to filter results based on a conditional.
Considering you want all entries rather than any given entry one that matches, you can use the following (written in MySQL) which uses a nested SELECT statement:
SELECT *
FROM Table
WHERE col3=(SELECT MAX(col3) FROM Table);
What is the best approach to append a row to a SQL Server query showing the total count of rows resulting from the query? UNION is one way, but seems very inefficient:
SELECT col1, col2 FROM tbl1
UNION ALL
SELECT STR(COUNT(col1)), NULL FROM tbl1
ROLLUP isn't an option because it requires GROUP BY, which we're not using for the queries in question.
You can use GROUPING SETS for this
SELECT
CASE WHEN GROUPING(col1) = 0 THEN col1 ELSE CAST(COUNT(*) AS varchar(30)) END AS col1,
col2
FROM tbl1
GROUP BY GROUPING SETS (
(col1, col2),
()
);
The GROUPING function will tell you whether the row is the Total row or not.
This does have the effect of grouping the columns which could be a different result and possibly less efficient. But if you include a unique/primary key as the first column in the grouping list then this shouldn't make a difference, and should be almost as performant as the original query.
You can also use a window function, which will return the total on each row as another column
SELECT
col1,
col2,
COUNT(*) OVER ()
FROM tbl1;
--mytable
col1 col2 col3
1 A red
2 A green
3 B purple
4 C blue
Let's call the table above mytable. I want to select only distinct values from col2:
SELECT DISTINCT
col2
FROM
mytable
When I do this the output looks like this, which is expected:
col2
A
B
C
but how do I perform the same type of query, yet keep all columns? The output would look like below. In essence I'm going through mytable looking at col2, and when there's multiple occurrences of col2 I'm only keeping the first row.
col1 col2 col3
1 A red
3 B purple
4 C blue
Do SQL functions (eg DISTINCT) have arguments I could set? I could imagine it to be something like KeepAllColumns = TRUE for this DISTINCT function? Or do I need to perform JOINs to get what I want?
You can use window functions, particularly row_number():
select t.*
from (select t.*, row_number() over (partition by col2 order by col2) as seqnum
from mytable t
) t
where seqnum = 1;
row_number() enumerates the rows, starting with "1". You can control whether you get the oldest, earliest, biggest, smallest . . .
You can use the QUALIFY clause in Teradata:
SELECT col1, col2, col3
FROM mytable
QUALIFY ROW_NUMBER() OVER(PARTITION BY col2 ORDER BY col2) = 1 -- Get 1st row per group
If you want to change the ordering for how to determine which col2 row to get, just change the expression in the ORDER BY.
With NOT EXISTS:
select m.* from mytable m
where not exists (
select 1 from mytable
where col2 = m.col2 and col1 < m.col1
)
This code will return the rows for which there is not another row with the same col2 and a smaller value in col1.
Really I don't know how to say it as question, but with example it will be clear to everyone, I have data retrieved from MYSQL database sorted by one of columns , my question if one of those values in this column is equal, I need to use another column to set who is show first.
col1 - col2
10 - 100
20 - 120
20 - 140
30 - 90
see here value 20 mentioned twice so I need to show the 20 with 140 before the 20 with 120 using MYSQL Query.
SELECT
*
FROM
MyTable
ORDER BY
Col1,
Col2 DESC
You can specify more than one column in the order by clause:
select * from table order by col1, col2;
This will order by col1, then order by col2 when col1 is equal. You can also specify ascending and descending separately for each column:
select * from table order by col1 asc, col2 desc;
You can add multiple columns in your order by clause.
select * from your_table
order by col1, col2 desc
The result will be ordered by the first column and if equal by the next and so forth
I am looking for something like rownum
You can use TOP, for example:
SELECT Top 10 col FROM Table ORDER BY col2
Note that this will return more than 10 records if col2 has duplicates.
Select Top n Col From Table