I Want to create a table in MySql for which has a column for Time
Value for time column must accept like 9AM to 10PM
+-----------------------------+
| DATE |
+-----------------------------+
| 9AM to 10PM |
+-----------------------------+
Which datatype should i use ?
If i don't want to use varcar & If i can use TIME data-type- How to represent values there ?
I am looking for create table and insert statement as an answer for above specifications ?
I am a newbie so please go easy with answers
Thanks !
As suggested above in comment the table structure would be:
Create Table YourTable
(
FromTime Time,
ToTime Time
)
Now Insert values as below:
Insert into yourTable
VALUES(TIME(STR_TO_DATE('09:00 AM', '%h:%i %p')),TIME(STR_TO_DATE('10:00 PM', '%h:%i %p')))
Use Time Data Type to save Time.
You can not insert 9AM to 10PM in datetime datatype column.
you have to use datatype whose representation should be like string, like varchar.
It's hard to tell exactly what you need based on what you've described - if you could provide a little more context we might be able to offer you more insight?
But as #rkp has mentioned, if you want the time interval to be represented as "9AM to 10PM", you will have to use some form of string/text field e.g. varchar
Alternatively, depending on how you plan to use this data, you could also use two fields - one for start time and one for end time. It would probably then be recommended that you use a datetime field since this will allow for much more flexibility (e.g. when calculating differences between time periods etc)
For reference - these are your options:
http://dev.mysql.com/doc/refman/5.0/en/date-and-time-types.html
Related
I have a column in a table that has dates, as such:
2010-01-15 00:00:00
2002-10-24 09:00:00
2015-04-29 10:00:00
and now I need to generate a new column as such (month, date, year):
01152010
10242002
04292015
I can't find an easy way to do this. All the solutions I've looked at are either for changing date type or getting seconds since epoch!
I've also tried all sorts of substring operations
You could try using the MySQL DateFormat Function.
The documentation is pretty a good resource for this sort of thing.
SELECT DATE_FORMAT(dateColumn, '%m%d%Y') As FormattedDate FROM <table>;
Here is an example I made using SQLFiddle.
I have created MySQL table :
CREATE TABLE EMP(
EMPID INTEGER NOT NULL (5),
SURNAME VARCHAR(25),
SAL INTEGER(5),
JON VARCHAR(25),
START_DATE DATE,
END_DATE DATE,
DEPNO INTEGER(5)
);
with following records:
INSERT INTO EMP
(EMPID,SURNAME,SALARY,JOB,START_DATE,END_DATE,DEPNO)
VALUES
('1','Vorosila','500000','COO','20150101',null,'1');
however I need to change date format from 2015 01 01 to 01 01 2015
Can anybody show me or tell me how to do that ?
THANK YOU IN ADVANCE
DATE values do not have a "format", they are objects that represent instants in time (or entire days, but still independent of formatting).
Formats are applied on input and output, so you just need to apply the correct format, which you can find in the MySQL manual, to the SELECT statement.
You cannot change the default date format in mysql.
I once hoped for the default date to be editable so I wouldn't have to jump through these hoops to get the date I actually wanted, mysql even has a date format system variable, but it is unused. Date Format Mysql - link
What you should really do is store it as the default format Year-Month-Date and then convert it on select.
The first thing I'd suggest is having your date columns as date types, which would give your dates the following format '2015-01-01'.
If you do this then you can use DATE_FORMAT - link - the second value in the DATE_FORMAT function allows you to customise the returned date, and there are many different thing you can do with this if you look at the link:
SELECT
DATE_FORMAT(`START_DATE`,'%d-%m-%Y')
AS `START_DATE`
FROM ...
The other option you have is to store your dates in the format that you already want as a char or varchar column.
HOWEVER, as should be obvious, this column will not be treated as storing dates, and so will not give you the correct comparisons in a where clause when using > < BETWEEN or the correct ordering in an order by clause. It is after all just a string of numbers in this case.
However you can then use STR_TO_DATE - link if you did need to use a where or order by on this column to change it back to a date within the query - in this case the second value is the custom format of your 'dates' in the column. Keep in mind with a where you will need to compare it with the correct mysql format as shown below:
SELECT
`START_DATE`
FROM table
WHERE STR_TO_DATE(`START_DATE`,'%d-%m-%Y') BETWEEN '2015-01-01' and '2016-01-01'
In MySQL you can change the format of a date using DATE_FORMAT method which is similar to to_char in Oracle.
DATE_FORMAT(SYSDATE(), '%DD-%MM-%YYYY');
For more information about specifiers check this thread http://www.sqlines.com/oracle-to-mysql/to_char_datetime
You can do what you probably want by creating a view and referring to that instead of the (underlying) table.
CREATE VIEW emp_view AS
SELECT empid,
surname,
sal,
jon,
date_format(start_date, '%d-%m-%Y') as start_date,
date_format(end_date, '%d-%m-%Y') as end_date,
depno
FROM emp;
Note that this changes the type of the date columns to varchar, so comparisons will no longer work as expected:
SELECT * FROM emp_view WHERE start_date > '01-12-1924'; // fails!
I have the following mysql table:
tasks:
=====================
tid
status
desc
duedate
And i have the following records in that table:
records
===========================
1
active
Test description
08/15/2014
2
active
Another description
08/31/204
I am trying to get the days that there is a task for, in that particular month. I have the following query but when i run it it gets both records but "day" is null on both of them for some reason. Can someone please help me with this.
MYSQL QUERY
====================
SELECT DATE_FORMAT(due_date,'%d') AS day FROM tasks WHERE due_date BETWEEN '08/01/2014' AND '08/31/2014'
Try:
SELECT DAY(due_date) AS day
FROM tasks
WHERE due_date >= '2014-08'
AND due_date < '2014-09';
DAY() is a better function for what you want and I prefer using >= and < than BETWEEN for date comparisons, as it allows you to specify precise ranges more easily. Here, for example, you don't need to know the number of days in the month.
I have also used the default date format, which is preferable. If you need the, in my opinion, cray American date format, use DATE_FORMAT() in your SELECT.
This will only work with DATE, DATETIME and TIMESTAMP columns, which is how your due_date should be stored, preferably DATE.
UPDATE
To convert the VARCHAR column to DATE run:
UPDATE tasks SET due_date=STR_TO_DATE(due_date,'%m/%d/%Y')
Then change the type. Also remember to change your INSERT statements to use the default format.
You've got to convert those "date" strings to proper date values with STR_TO_DATE:
SELECT
DAY(STR_TO_DATE(due_date,'%m/%d/%Y')) AS day
FROM tasks
WHERE
STR_TO_DATE(due_date, '%m/%d/%Y')
BETWEEN STR_TO_DATE('08/01/2014' '%m/%d/%Y')
AND STR_TO_DATE('08/31/2014', '%m/%d/%Y')
else you're comparing strings instead.
Note:
It would be better to use a proper DATE or DATETIME column instead.
With the current VARCHAR format MySQL is unable to use indexes. That's very bad for performance.
You can convert your data by adding another column to your table:
ALTER TABLE tasks
ADD COLUMN new_due_date DATE;
Then you use an UPDATE statement to fill this new column
UPDATE tasks
SET new_due_date = STR_TO_DATE(due_date, '%m/%d/%Y');
If you don't need your old column anymore then you can delete this column and modify the new column to have the name of the old one. Then you will have your table with all your data in a DATE column.
I generally use datetime field to store created_time updated time of data within an application.
But now i have come across a database table where they have kept date and time separate fields in table.
So what are the schema in which two of these should be used and why?
What are pros and cons attached with using of two?
There is a huge difference in performance when using DATE field above DATETIME field. I have a table with more then 4.000.000 records and for testing purposes I added 2 fields with both their own index. One using DATETIME and the other field using DATE.
I disabled MySQL query cache to be able to test properly and looped over the same query for 1000x:
SELECT * FROM `logs` WHERE `dt` BETWEEN '2015-04-01' AND '2015-05-01' LIMIT 10000,10;
DATETIME INDEX:
197.564 seconds.
SELECT * FROM `logs` WHERE `d` BETWEEN '2015-04-01' AND '2015-05-01' LIMIT 10000,10;
DATE INDEX:
107.577 seconds.
Using a date indexed field has a performance improvement of: 45.55%!!
So I would say if you are expecting a lot of data in your table please consider in separating the date from the time with their own index.
I tend to think there are basically no advantages to storing the date and time in separate fields. MySQL offers very convenient functions for extracting the date and time parts of a datetime value.
Okay. There can be some efficiency reasons. In MySQL, you can put separate indexes on the fields. So, if you want to search for particular times, for instance, then a query that counts by hours of the day (for instance) can use an index on the time field. An index on a datetime field would not be used in this case. A separate date field might make it easier to write a query that will use the date index, but, strictly speaking, a datetime should also work.
The one time where I've seen dates and times stored separately is in a trading system. In this case, the trade has a valuation date. The valuation time is something like "NY Open" or "London Close" -- this is not a real time value. It is a description of the time of day used for valuation.
The tricky part is when you have to do date arithmetic on a time value and you do not want a date portion coming into the mix. Ex:
myapptdate = 2014-01-02 09:00:00
Select such and such where myapptdate between 2014-01-02 07:00:00 and 2014-01-02 13:00:00
1900-01-02 07:00:00
2014-01-02 07:00:00
One difference I found is using BETWEEN for dates with non-zero time.
Imagine a search with "between dates" filter. Standard user's expectation is it will return records from the end day as well, so using DATETIME you have to always add an extra day for the BETWEEN to work as expected, while using DATE you only pass what user entered, with no extra logic needed.
So query
SELECT * FROM mytable WHERE mydate BETWEEN '2020-06-24' AND '2020-06-25'
will return a record for 2020-06-25 16:30:00, while query:
SELECT * FROM mytable WHERE mydatetime BETWEEN '2020-06-24' AND '2020-06-25'
won't - you'd have to add an extra day:
SELECT * FROM mytable WHERE mydatetime BETWEEN '2020-06-24' AND '2020-06-26'
But as victor diaz mentioned, doing datetime calculations with date+time would be a super inefficient nightmare and far worse, than just adding a day to the second datetime. Therefore I'd only use DATE if the time is irrelevant, or as a "cache" for speeding queries up for date lookups (see Elwin's answer).
What's the best way to store a date value for which in many cases only the year may be known?
MySQL allows zeros in date parts unless the NO_ZEROES_IN_DATE sql mode is enabled, which isn't by default. Is there any reason not to use a date field where if the month and day may be zero, or to split it up to 3 different fields for year, month and day (year(4), tinyint, tinyint)?
A better way is to split the date into 3 fields. Year, Month, Day. This gives you full flexibility for storing, sorting, and searching.
Also, it's pretty trivial to put the fields back together into a real date field when necessary.
Finally, it's portable across DBMS's. I don't think anyone else supports a 0 as a valid part of a date value.
Unless portability across DBMS is important, I would definitely be inclined to use a single date field. If you require even moderately complex date related queries, having your day, month and year values in separate fields will become a chore.
MySQL has a wealth of date related functions - http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html. Use YEAR(yourdatefield) if you want to return just the year value, or the same if you want to include it in your query's WHERE clause.
You can use a single date field in Mysql to do this. In the example below field has the date data type.
mysql> select * from test;
+------------+------+
| field | id |
+------------+------+
| 2007-00-00 | 1 |
+------------+------+
1 row in set (0.00 sec)
mysql> select * from test where YEAR(field) = 2007;
+------------+------+
| field | id |
+------------+------+
| 2007-00-00 | 1 |
+------------+------+
I would use one field it will make the queries easier.
Yes using the Date and Time functions would be better.
Thanks BrynJ
You could try a LIKE operative. Such as:
SELECT * FROM table WHERE date_feield LIKE 2009;
It depends on how you use the resulting data. A simple answer would be to simply store those dates where only the year is known as January 1. This approach is really simple and allows you to aggregate by year using all the standard built in date functions.
The problem arises if the month or date is significant. For example if you are trying to determine the age of a record in days, weeks, months or if you want to show distribution across this smaller level of granularity. This problem exists any way, though. If you have some full dates and some with only a year, how do you want to represent them in such instances.