How do I combine the calculation date columns all into one column? What's the SQL function to make this happen? They rest of the fields are distinct values based on the calculation date. I only need the distinct values associated with the dates.
EDIT
I tried the ISNULL and COALESCE functions and this is not what I'm looking for because it still brings back all the values for both of the dates. I only need the data as of the date for select accounts. I don't want the data for both dates on the same account.
I also tried the Select Distinct and it's not working for me.
You can use COALESCE
SELECT COALESCE(Calculation_Date, Calculation_Date)
FROM tableName
Assuming only 1 of them will ever have a value, one option is to use coalesce:
select coalesce(date1, date2)
from yourtable
Since you have only two columns, an alternative is to use ISNULL:
SELECT ISNULL(FIRST_CALCULATION_DATE, SECOND_CALCULATION_DATE) AS ActualCalculationDate
FROM TheTable
You should receive the same results as for COALESCE, but it is interesting to know that there are some subtle differences between them when it comes to determining result type.
Related
i am trying to count the number of records in the particular date.
eventually, got the query worked but confused between these two queries which seemed to same for me. why should i enclose the date_time instead of quote in the conversion.
when i hit the query,
select count(*) from TABLENAME
where FROM_UNIXTIME(UNIX_TIMESTAMP(date_time), 'yyyyMMdd')='20170312';
result is count of the particular date is arrived.
but when i hit,
select count(*) from TABLENAME
where FROM_UNIXTIME(UNIX_TIMESTAMP('date_time', 'yyyyMMdd'))='20170312';
the result is 0.
please explain the difference of these queries.
date_time is a column while 'date_time' is a string and the attempt to use it as date result in NULL.
If you want to qualify the column name you should use `date_time`
Needs help in sql:
I need to group max online of each day by days
(http://prntscr.com/a7j2sm)
my sql select:
SELECT id, date, MAX(online)
FROM `record_online_1`
GROUP BY DAY(date)
and result - http://prntscr.com/a7j3sp
This is incorrect result because, max online is correct, but date and id of this top online is incorrect. I dont have ideas how solve this issue..
UPD: using MySQL MariaDB
When you perform an aggregate functions, you have to include items in the SELECT statement that aren't a part of an aggregate function in the GROUP BY clause. In T-SQL, you simply cannot execute the above query if you don't also GROUP BY "id" for example. However, some database systems allow you to forego this rule, but it's not smart enough to know which ID it should bring back to you. You should only be doing this if, for example, all "ids" for that segment are the same.
So what should you do? Do this in two steps. Step one, find the max values. You will lose the ID and DATETIME data.
SELECT DAY(date) AS Date, MAX(online) AS MaxOnline
FROM `record_online_1` GROUP BY DAY(date)
The above will get you a list of dates with the max for each day. INNER JOIN this to the original "record_online_1" table, joining specifically on the date and max value. You can use a CTE, temp table, subquery, etc to do this.
EDIT: I found an answer that is more eloquent than my own.
At my office, one of the tables we use keeps track of our Order Numbers. The problem is that the employees don't enter the number consistantly into the database field.
Some of the examples are listed:
'7-26-13 543006-27031', '345009-27031', 'KWYD-863009-27031'.
I need to to find a way to return just the 'nnnnnn-nnnnn' substring
no matter where in the field it is. Most of the time, this pattern is at the end of the field, but that is not always the case. I've already limited the data records to just those with that pattern using a LIKE expression in my WHERE clause, but I have no idea how to best return just that pattern as a column.
Edit:
We are still using SQL Server 2000
What I'm looking to do is along the lines of:
SELECT SUBSTRING(VendorOrderNo, ??, 12) AS OrderNo
FROM Orders
WHERE VendorOrderNo LIKE '%[0-9][0-9][0-9][0-9][0-9][0-9]-[0-9][0-9][0-9][0-9][0-9]%'
select 'nnnnnn-nnnnn' as employeeid
from table
where employees like'%nnnnnn-nnnnn'
It would be better if you adjust your data first, you can give this a try (its for MYSQL)
SELECT * FROM your_table_name WHERE order_number REGEXP '[0-9]+-[0-9]+';
SQLFIDDLE
In my SQL query I just need to check whether data exists for a particular userid.
I always only want one row that will be returned when data exist.
I have two options
1. select count(columnname) from table where userid=:userid
2. select count(1) from tablename where userid=:userid
I am thinking second one is the one I should use because it may have a better response time as compared with first one.
There can be differences between count(*) and count(column). count(*) is often fastest for reasons discussed here. Basically, with count(column) the database has to check if column is null or not in each row. With count(column) it just returns the total number of rows in the table which is probably has on hand. The exact details may depend on the database and the version of the database.
Short answer: use count(*) or count(1). Hell, forget the count and select userid.
You should also make sure the where clause is performing well and that its using an index. Look into EXPLAIN.
I'd like to point out that this:
select count(*) from tablename where userid=:userid
has the same effect as your second solution, with th advantage that count(*) it unambigously means "count all rows".
The * in COUNT(*) will not expand into all columns - that is to say, the * in SELECT COUNT(*) is not the same as in SELECT *. So you need not worry about performance when writing COUNT(*)
The disadvantage of writing COUNT(1) is that it is less clear: what did you mean? A literal one (1) may look like a lower case L (this: l) in some fonts.
Will give different results if columnname can be NULL, otherwise identical performance.
The optimiser (SQL Server at least) realises COUNT(1) is trivial. You can also use COUNT(1/0)
It depends what you want to do.
The first one counts rows with non-null values of columnname. The second one counts ALL rows.
Which behaviour do you want? From the way your question is worded, I guess that you want the second one.
To count the number of records you should use the second option, or rather:
select count(*) from tablename where userid=:userid
You could also use the exists() function:
select case when exists(select * from tablename where userid=:userid) then 1 else 0 end
It might be possible for the database to do the latter more efficiently in some cases, as it can stop looking as soon as a match is found instead of comparing all records.
Hey how about Select count(userid) from tablename where userid=:userid ? That way the query looks more friendly.
Is there a another way to subtract the smallest value from all the values of a column, effectively offset the values?
The only way I have found becomes horribly complicated for more complex queries.
CREATE TABLE offsettest(value NUMBER);
INSERT INTO offsettest VALUES(100);
INSERT INTO offsettest VALUES(200);
INSERT INTO offsettest VALUES(300);
INSERT INTO offsettest VALUES(400);
SELECT value - (SELECT MIN(value) FROM offsettest) FROM offsettest;
DROP TABLE offsettest;
I'd like to limit it to a single query (no stored procedures, variables, etc) if possible and standard SQL is preferred (although I am using Oracle).
I believe this works as of ANSI 1999.
SELECT value - MIN(value) OVER() FROM offsettest;
It would have helped you see your actual query, though, since depending on whether you need to manipulate more than one column this way, and the various minimums come from different rows, there may be more efficient ways to do it. If the OVER() works for you, then fine.