Using Postgres, but if someone knows how to do this in standard SQL that would be a great start. I am joining to a table via a character varying column. This column contains values such as:
PC11941.2004
PC14151.2004
PC21213.2003
SPC21434.2003
PC17715.04V1
PC18733.2002
0MRACCT_ALL.GLFUNCT
A lot of the numbers after the periods correspond to years. I want to join the table via the current year. So, for example, I could JOIN on the condition LIKE '%2015'.
But I want to create this view and never return to it so I would need to join it against something like (get_fy_part('YEAR', clock_timestamp()).
Not sure how I go about writing that. I haven't had success, yet.
You can get the current year with date_part('year', CURRENT_DATE)
Something like this should work:
SELECT * FROM mytable WHERE mycolumn LIKE ('%' || date_part('year', CURRENT_DATE))
The || operator concatenates the percent-sign with the year.
I hope that helps!
Use the function RIGHT().
SELECT originalColumn, RIGHT(originalColumn,4)
FROM table;
This will get you the years you are interested in.
If you want everything after the dot, then something like:
SELECT originalColumn, RIGHT(originalColumn,len(originalColumn)-position('.' in originalColumn))
FROM table
Depends on the exact rules - and actually implemented CHECK constraints for the column.
If there is always a single dot in your column col and all your years have 4 digits:
Basic solution
SELECT * FROM tbl
WHERE col LIKE to_char(now(), '"%."YYYY');
Why?
It's most efficient to compare to the same data type. Since the column is a character type (varchar), rather use to_char() (returns text, which is effectively the same as varchar) than EXTRACT or date_part() (return double precision).
More importantly, this expression is sargable. That's generally cheapest and allows (optional) index support. In your case, a trigram index would work:
PostgreSQL LIKE query performance variations
Optimize
If you want to be as fast (read performance) and accurate as possible, and your table has more than a trivial number of rows, go with a specialized partial expression index:
CRATE INDEX tbl_year_idx ON tbl (cast(right(col, 4) AS int) DESC)
WHERE col ~ '\.\d{4}$'; -- ends with a dot and 4 digits
Matching query:
SELECT * FROM tbl
WHERE col ~ '\.\d{4}$' -- repeat index condition
AND right(col, 4)::int = EXTRACT(year FROM col);
Test performance with EXPLAIN ANALYZE.
You could even go one step further and tailor the index for the current year:
CRATE INDEX tbl_year2015_idx ON tbl (tbl_id) -- any (useful?) column
WHERE col LIKE '%.2015';
Works with the first "basic" query.
You would have to (re-)create the index for each year. A simple solution would be to create indexes for a couple of years ahead and append another one each year automatically ...
This is also the point where you consider the alternative: store the year as redundant integer column in your table and simplify the rest.
That's what I would do.
Related
I need to a value associated to a month and a user in a table. And I want to perform queries on it. I don't know if there is a column data type for this type of need. If not, should I:
Create a string field and build year-month concatenation (2017-01)
Create a int field and build year-month concatenation (201701)
Create two columns (one year and one month)
Create a date column at the beginning of the month (2017-01-01 00:00:00)
Something else?
The objective is to run queries like (pseudo-SQL):
SELECT val FROM t WHERE year_month = THIS_YEAR_MONTH and user_id='adc1-23...';
I would suggest not thinking too hard about the problem and just using the first date/time of the month. Postgres has plenty of date-specific functions -- from date_trunc() to age() to + interval -- to support dates.
You can readily convert them to the format you want, get the difference between two values, and so on.
If you phrase your query as:
where year_month = date_trunc('month', now()) and user_id = 'adc1-23...'
Then it can readily take advantage of an index on (user_id, year_month) or (year_month, user_id).
If you are interested in display values in YYYY-MM formt you can use to_char(your_datatime_colum,'YYYY-MM')
example:
SELECT to_char(now(),'YYYY-MM') as year_month
I am trying to write a query that gets all the rows of a table for a particular date.
SELECT * FROM MY_TABLE WHERE COLUMN_CONTAINING_DATE='2013-05-07'
However that does not work, because in the table the COLUMN_CONTAINING_DATE contains data like '2013-05-07 00:00:01' etc. So, this would work
SELECT * FROM MY_TABLE WHERE COLUMN_CONTAINING_DATE>='2013-05-07' AND COLUMN_CONTAINING_DATE<'2013-05-08'
However, I dont want to go for option 2 because that feels like a hacky way. I would rather put a query that says get me all the rows for a give date and somehow not bother about the minutes and hours in the COLUMN_CONTAINING_DATE.
I am trying to have this query run on both H2 and DB2.
Any suggestions?
You can do:
select *
from MY_Table
where trunc(COLUMN_CONTAINING_DATE) = '2013-05-07';
However, the version that you describe as a "hack" is actually better. By wrapping a function around the data, many SQL optimizers will not use indexes. With just direct comparisons, an index would definitely be used.
Use something like this
SELECT * FROM MY_TABLE WHERE COLUMN_CONTAINING_DATE=DATE('2013-05-07')
You can ease this if you use the Temporal data management capability from DB2 10.1.
For more information:
http://www.ibm.com/developerworks/data/library/techarticle/dm-1204db2temporaldata/
If your concerns are related to the different data types (timestamp in the column, and a string containing a date), you can do this:
SELECT * FROM MY_TABLE
WHERE
COLUMN_CONTAINING_DATE >= '2013-05-07 00:00:00'
and COLUMN_CONTAINING_DATE < '2013-05-08 00:00:00'
and I'd pay attention to the formatting of the where clause, because this will improve readability a lot, if you have to look at your queries two months later. Just pick a style you prefer for ranges like "a <= x < b". Unfortunately SQL's between does not support this.
One could argue that the milliseconds are still missing, so perfectionists may append another ".0" in the timestamp ...
I have a date of birth DATE column in a customer table with ~13 million rows. I would like to query this table to find all customers who were born on a certain month and day of that month, but any year.
Can I do this by casting the date into a char and doing a subscript query on the cast, or should I create an aditional char column, update it to hold just the month and day, or create three new integer columns to hold month, day and year, respectively?
This will be a very frequently used query criteria...
EDIT:... and the table has ~13 million rows.
Can you please provide an example of your best solution?
If it will be frequently used, consider a 'functional index'. Searching on that term at the Informix 11.70 InfoCentre produces a number of relevant hits.
You can use:
WHERE MONTH(date_col) = 12 AND DAY(date_col) = 25;
You can also play games such as:
WHERE MONTH(date_col) * 100 + DAY(date_col) = 1225;
This might be more suitable for a functional index, but isn't as clear for everyday use. You could easily write a stored procedure too:
Note that in the absence of a functional index, invoking functions on a column in the criterion means that an index is unlikely to be used.
CREATE FUNCTION mmdd(date_val DATE DEFAULT TODAY) RETURNING SMALLINT AS mmdd;
RETURN MONTH(date_val) * 100 + DAY(date_val);
END FUNCTION;
And use it as:
WHERE mmdd(date_col) = 1225;
Depending on how frequently you do this and how fast it needs to run you might think about splitting the date column into day, month and year columns. This would make search faster but cause all sorts of other problems when you want to retrieve a whole date (and also problems in validating that it is a date) - not a great idea.
Assuming speed isn't a probem I would do something like:
select *
FROM Table
WHERE Month(*DateOfBirthColumn*) = *SomeMonth* AND DAY(*DateOfBirthColumn*) = *SomeDay*
I don't have informix in front of me at the moment but I think the syntax is right.
I'm blacking out on my basic SQL and would appreciate a quick hand:
I have a SQLite table, with 2 columns: Datetime, and a string saying something like "call from 555-555-3344".
I need a simple query that will give me a count of all distinct phone numbers that called on a certain day.
If the field had contained just the number, I could have used Select Distinct on it. How do I do it if the value (phone number) is a substring in that field (though always the last 10 digits).
Assistance, as always, much appreciated.
Guy
You can use the following (I used 12 instead of 10 in order to include the separator -):
SELECT COUNT(DISTINCT SUBSTR(phone_nbr, -12))
FROM table
WHERE call_dt = :call_dt;
Can I do WHERE operations on a calculated date field?
I have a lookup field, which has been written badly in SQL and unfortunately I can't change it. But basically it stores dates as characters such as "July-2010" or "June-2009" (along with other non date data). I want to extract the dates first (which I did using a LIKE opertor) and then extract data based on a date range.
SELECT
BusinessUnit,
Lookup,
ReleaseDate
FROM
(
SELECT TOP 10
LookupColumn As Lookup,
BU as BusinessUnit,
CONVERT(DATETIME, REPLACE(LookupColumn,'-',' ')) as ReleaseDate
FROM
[dbo].[LookupTable]
WHERE
LookupColumn LIKE N'%-2010'
) MyTable
ORDER BY ReleaseDate
WHERE ReleaseDate = '2010-02-01'
I'm having issues with WHERE operator. I would assume creating a subquery to encapsulate the calculated field would allow me to do operations with it such as WHERE but maybe I'm wrong. Bottom line is it possible to do operations on calculated fields?
UPDATE: indeed I had the order mixed up and furthermore the LIKE operator was also returning non-date values such as TBD-2010 which were messing me up.
You have the ORDER BY and WHERE clauses round the wrong way. Try switching them round:
...
) MyTable
WHERE ReleaseDate = '2010-02-01'
ORDER BY ReleaseDate
You'd probably have an easier time encapsulating this table in a view and then querying the view. This way, your view alone contains the logic to convert this bit of awfulness into a normal DATETIME column.
What "issues" are you having?
In your example, you can't have a WHERE clause AFTER an ORDER BY clause...