I have a query that requires a where statement on a calculated value:
select * from table where date( timestamp ) = ?
An explain on this query yields the expected ALL select type, which is not ideal. Using MySQL, what's the best way to optimize this?
Another option might be to rewrite the query such that the calculations are all done on the other side of the equation. For example:
timestamp >= <some date> AND timestamp < <some date + 1>
In this query, "some date" would be midnight of that date.
select * from table where timestamp = UNIX_TIMESTAMP('?');
Related
So, i´m trying to select rows between two dates.
In db, the dates also have time.
Therefor i need to use LIKE.
SQL
$query = "SELECT * FROM table WHERE date >= LIKE :selectedDateFrom AND <= LIKE :selectedDateTo";
$query_params = array(':selectedDateFrom' => $selectedDateFrom.="%", ':selectedDateTo' => $selectedDateTo.="%");
This one returns error!
How should it look like?
In db, the dates also have time.
Therefor i need to use LIKE.
No, you don't.
To select all date/times where the date component is between (from) and (to), inclusive, you can write it as
SELECT *
FROM table
WHERE date >= :selectedDateFrom
AND date < :selectedDateToPlusOne
(Note the < instead of <=, and set the second parameter to one day after the last day you want to include in your results.) This works even when the column includes times.
you can't use like with dates in SQL
SO use this:
$query = "SELECT * FROM table WHERE date >= :selectedDateFrom AND date <= :selectedDateTo";
You'd strip the time part from a datetime with DATE().
SELECT *
FROM mytable
WHERE date(mydate) >= :selectedDateFrom
AND date(mydate) <= :selectedDateTo;
Or with BETWEEN for better readability:
SELECT *
FROM mytable
WHERE date(mydate) BETWEEN :selectedDateFrom AND :selectedDateTo;
I have a table for matches. The table has a column named matchdate, which is a datetime field.
If I have 3 matches on 2011-12-01:
2011-12-01 12:00:00
2011-12-01 13:25:00
2011-12-01 16:00:00
How do I query that? How do I query all matches on 1 single date?
I have looked at date_trunc(), to_char(), etc.
Isn't there some "select * where datetime in date" function?
Cast your timestamp value to date if you want simple syntax. Like this:
SELECT *
FROM tbl
WHERE timestamp_col::date = '2011-12-01'; -- date literal
However, with big tables this will be faster:
SELECT *
FROM tbl
WHERE timestamp_col >= '2011-12-01 0:0' -- timestamp literal
AND timestamp_col < '2011-12-02 0:0';
Reason: the second query does not have to transform every single value in the table and can utilize a simple index on the timestamp column. The expression is sargable.
Note excluded the upper bound (< instead of <=) for a correct selection.
You can make up for that by creating an index on an expression like this:
CREATE INDEX tbl_ts_date_idx ON tbl (cast(timestamp_col AS date));
Then the first version of the query will be as fast as it gets.
not sure if i am missing something obvious here, but i think you can just
select * from table where date_trunc('day', ts) = '2011-12-01';
Just use the SQL BETWEEN function like so:
SELECT * FROM table WHERE date BETWEEN '2011-12-01' AND '2011-12-02'
You may need to include times in the date literals, but this should include the lover limit and exclude the upper.
From rails I believe you can do:
.where(:between => '2011-12-01'..'2011-12-02')
My table has records like these
23-MAY-11 11.40.39.000000 AM
The following query brings nothing
SELECT *
FROM my_table
WHERE tenant_pha = 'test'
AND create_date >= TO_DATE('05/10/2011','mm/dd/yyyy')
AND create_date <= TO_DATE('05/23/2011','mm/dd/yyyy')
However, the below query will bring data
SELECT *
FROM my_table
WHERE tenant_pha = 'test'
AND create_date >= TO_DATE('05/10/2011','mm/dd/yyyy')
AND create_date <= TO_DATE('05/24/2011','mm/dd/yyyy')
I think this is because create_date column is time stamp.
How can I change my query to bring the desired result ( I want to avoid doing functions on the left side columns because they will make the query long).
You are right about the timestamp. '05/23/2011' is the same as '05/23/2011 12:00 AM'.
To include the whole day I usually move my date up by a day. < '05/24/2011' will include all of 5/23.
or change to '05/23/2011 23:59:59'
You can use trunc() without problems, you only need to create a function based index.
If you create this index:
CREATE INDEX idx_trunc_date ON my_table (trunc(create_date));
then the following condition will make use of that index:
AND trunc(create_date) >= TO_DATE('05/10/2011','mm/dd/yyyy')
Suppose I have a date 2010-07-29. Now I would like to check the result of one day ahead. how to do that
For example,
SELECT *
from table
where date = date("2010-07-29")
How to do one day before without changing the string "2010-07-29"?
I searched and get some suggestion from web and I tried
SELECT *
from table
where date = (date("2010-07-29") - 1 Day)
but failed.
MySQL
SELECT *
FROM TABLE t
WHERE t.date BETWEEN DATE_SUB('2010-07-29', INTERVAL 1 DAY)
AND '2010-07-29'
Change DATE_SUB to DATE_ADD if you want to add a day (and reverse the BETWEEN parameters).
SQL Server
SELECT *
FROM TABLE t
WHERE t.date BETWEEN DATEADD(dd, -1, '2010-07-29')
AND '2010-07-29'
Oracle
SELECT *
FROM TABLE t
WHERE t.date BETWEEN TO_DATE('2010-07-29', 'YYYY-MM-DD') - 1
AND TO_DATE('2010-07-29', 'YYYY-MM-DD')
I used BETWEEN because the date column is likely DATETIME (on MySQL & SQL Server, vs DATE on Oracle), which includes the time portion so equals means the value has to equal exactly. These queries give you the span of a day.
If you're using Oracle, you can use the + and - operators to add a number of days to a date.
http://psoug.org/reference/date_func.html
Example:
SELECT SYSDATE + 1 FROM dual;
Will yield tomorrow's date.
If you're not using Oracle, please tell use what you ARE using so we can give better answers. This sort of thing depends on the database you are using. It will NOT be the same across different databases.
Depends of the DateTime Functions available on the RDBMS
For Mysql you can try:
mysql> SELECT DATE_ADD('1997-12-31',
-> INTERVAL 1 DAY);
mysql> SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
-> '1997-12-02'
If youre using MSSQL, you're looking for DateAdd() I'm a little fuzzy on the syntax, but its something like:
Select * //not really, call out your columns
From [table]
Where date = DateAdd(dd, -1, "2010-07-29",)
Edit: This syntax should be correct: it has been updated in response to a comment.
I may have the specific parameters in the wrong order, but that should get you there.
In PL SQL : select sysdate+1 from dual;
I'm currently trying to optimize a MYSQL statement that is taking quite some time. The table this is running on is 600k+ and the query is taking over 10 seconds.
SELECT DATE_FORMAT( timestamp, '%Y-%m-%d' ) AS date, COUNT( DISTINCT (
email
) ) AS count
FROM log
WHERE timestamp > '2009-02-23'
AND timestamp < '2020-01-01'
AND TYPE = 'play'
GROUP BY date
ORDER BY date DESC
I've just indexes on timestamp and type and also one on timestamp_type (type_2).
Here is the explain results, the problem seems to be a file sort but I don't know how to get around this...
id: 1
select_type: SIMPLE
table: log
type: ref
possible_keys: type,timestamp,type_2
key: type_2
key_len: 1
ref: const
rows: 226403
Extra: Using where; Using filesort
Thanks
Things to try:
Have a separate date column (indexed) and use that instead of your timestamp column
Add an index across type and date
Use BETWEEN (don't think it will affect the speed but it's easier to read)
So ideally you would
Create a date column and fill it using UPDATE table SET date = DATE(timestamp)
Index across type and date
Change your select to ... type = ? AND date BETWEEN ? AND ?
Try rewriting to filter on TYPE alone first. Then apply your date range and aggregates. Basically create an inline view that filters type down. I know it's likely that the optimizer is doing this already, but when trying to improve performance I find it's helpful to be very certain of what things are happening first.
DATE_FORMAT will not utilizing the indexes.
You can still use the below query to utilize the index on timestamp column
SELECT timestamp AS date, COUNT( DISTINCT (
email
) ) AS count
FROM log
WHERE timestamp > '2009-02-23 00:00:00'
AND timestamp < '2020-01-01 23:59:59'
AND TYPE = 'play'
GROUP BY date
ORDER BY date DESC
Format the datetime value to date while printing/using