For some reasons it seems that the rows are not being updated. Any idea why this would happen ?
UPDATE hts SET assigned='1' AND Owner='ms' WHERE hid='217477'
Query OK, 0 rows affected (0.16 sec)
Rows matched: 1 Changed: 0 Warnings: 0
select assigned, Owner from hts where hid='217477';
+----------+-------+
| assigned | Owner |
+----------+-------+
| NULL | NULL |
+----------+-------+
Show columns from hts
+------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| hid | varchar(25) | YES | UNI | NULL | |
| assigned | int(11) | NO | | 0 | |
| Owner | varchar(10) | YES | | NULL | |
+------------+--------------+------+-----+---------+-------+
two things you can try..
first try removing the AND from the SET.. usually you do that with a comma..
UPDATE hts SET assigned=1, Owner='ms' WHERE hid='217477'
second try removing the quotes form the hid if it is an INT and not a VARCHAR
UPDATE hts SET assigned=1, Owner='ms' WHERE hid=217477
not sure why you are storing integers as strings.. when in doubt you should ALWAYS store data by its intended datatype.
RECOMMENDATION: change the datatypes if they are varchar to int. your update would look like this.
UPDATE hts SET assigned=1, Owner='ms' WHERE hid=217477
assigned should be integer as well as hid
Related
I am currently learning the basics of creating a database and doing some line of data analysis. i have been struggling to understand how to 'start coding'
so i finally decided to come up with a simple diary project to kick start my coding life.
Here is what i have so far, in terms of python so far nothing except i managed to link python and mysql.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| diary |
| mysql |
| performance_schema |
| sakila |
| sys |
| world |
+--------------------+
7 rows in set (0.00 sec)
mysql> desc diary;
+---------------+--------------+------+-----+-------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------+--------------+------+-----+-------------------+-------+
| TASK_COMMENTS | varchar(255) | YES | | NULL | |
| TASK | varchar(55) | NO | | NULL | |
| TS | timestamp | NO | | CURRENT_TIMESTAMP | |
+---------------+--------------+------+-----+-------------------+-------+
3 rows in set (0.00 sec)
mysql> select * from diary;
+---------------+---------------+---------------------+
| TASK_COMMENTS | TASK | TS |
+---------------+---------------+---------------------+
| NULL | Food Shopping | 2016-12-25 18:53:32 |
+---------------+---------------+---------------------+
1 row in set (0.00 sec)
here is the question finally:): Is it correct if i make the time stamp a primary key or is it more 'database error-free' to create an actual id instead of using automated timestamp as the pk?
also i am trying to make TASK_COMMENTS field not null aswell but i get this:
mysql> ALTER TABLE Diary MODIFY COLUMN TASK_COMMENTS VARCHAR(255) NOT NULL;
ERROR 1138 (22004): Invalid use of NULL value
Thank you for helping.
You can't alter the default value of a column to NOT NULL if a NULL value already exists. Either delete the row, or set it to something, then you can alter the column.
Using a timestamp is not a good idea for a primary key because it is very possible to get duplicate values. It's also easy not to, but it's just not a good idea. Use an id column, set the PK, and typically one would give it AUTO INCREMENT to ensure no duplicates.
I have a table of this structure:
mysql> desc securities;
+-----------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+-------------+------+-----+---------+-------+
| sym | varchar(19) | NO | PRI | | |
| bqn | int(11) | YES | | NULL | |
| sqn | int(11) | YES | | NULL | |
| tqn | int(11) | YES | | NULL | |
+-----------------+-------------+------+-----+---------+-------+
4 rows in set (0.01 sec)
I am trying to do a select and an update within the same query, so the reason I have chosen
insert into securities (sym, bqn, sqn , tqn) values('ANK', 50,0,1577798)
on duplicate key update bqn=bqn+50 , sqn=sqn+0 , tqn=tqn+1577798;
When I ran the above I observed it is in fact changing the values for all the other rows also.
Is this behaviour expected? I am using MySQL Database.
Your fiddle is missing the key, and the INSERT statement in the right panel (where it does not belong in the first place) is using different column names … *sigh*
Define the symbol column as PRIMARY KEY – and use the VALUES() syntax to get the values to add in the ON UPDATE part, so that you don’t have to repeat them every single time:
insert into securities
(symbol, buyerquan, sellerquan , totaltradedquan)
values('BANKBARODA', 73, 0, 4290270)
on duplicate key update
buyerquan=buyerquan+VALUES(buyerquan),
sellerquan=sellerquan+VALUES(sellerquan),
totaltradedquan=totaltradedquan+VALUES(totaltradedquan);
Works perfectly fine, result values are as to be expect from the input: http://sqlfiddle.com/#!2/21638f/1
Here is my code to delete my first row.
But not effected!
mysql> select * from myt;
+--------+--------------+------+---------+
| Fname | Lname | age | phone |
+--------+--------------+------+---------+
| NULL | Jackson | NULL | NULL |
| stive | NULL | NULL | NULL |
| ghbfgf | rtrgf | 22 | 111 |
| zxas | zxa | 30 | 6547812 |
| wewew | uytree | 22 | 658478 |
+--------+--------------+------+---------+
5 rows in set (0.00 sec)
mysql> delete from myt
-> Where Fname = "NULL";
Query OK, 0 rows affected (0.00 sec)
Thanks!
use IS NULL.
You cannot use arithmetic comparison operators such as =, <, or <> to test for NULL.
DELETE FROM myt WHERE Fname IS NULL
Working with NULL Values
NULL is not a value.
NULL means nothing is present.
So usage of FNAME = "NULL" is wrong.
delete from myt Where Fname IS NULL;
Your first row is NULL (none) not "NULL"
NULL is not a value in RDBMS; it is a marker for a missing value. When you are using "NULL" it denotes a string value. You can simply use "IS NULL". Hope this helps.
I have the following table:
mysql> DESC my_contacts;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | varchar(20) | NO | PRI | | |
| location | varchar(20) | YES | | NULL | |
| city | varchar(20) | YES | | NULL | |
| state | varchar(2) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
4 rows in set (0.01 sec)
If I do a select all I get:
mysql> SELECT * FROM my_contacts;
+----+--------------+------+-------+
| id | location | city | state |
+----+--------------+------+-------+
| 1 | Chester,NJ | NULL | NULL |
| 2 | Katy,TX | NULL | NULL |
| 3 | San Mateo,CA | NULL | NULL |
+----+--------------+------+-------+
3 rows in set (0.00 sec)
I run the following command:
INSERT INTO my_contacts (city,state)
VALUES
(SUBSTRING_INDEX(location,',',1),RIGHT(location,2));
My purpose was to populate the columns city and state with the part before the comma and the part after the comma from the location column.
But the following happened to my table:
mysql> INSERT INTO my_contacts (city,state)
-> VALUES
-> (SUBSTRING_INDEX(location,',',1),RIGHT(location,2));
Query OK, 1 row affected (0.02 sec)
mysql> SELECT * FROM my_contacts;
+----+--------------+------+-------+
| id | location | city | state |
+----+--------------+------+-------+
| | NULL | NULL | NULL |
| 1 | Chester,NJ | NULL | NULL |
| 2 | Katy,TX | NULL | NULL |
| 3 | San Mateo,CA | NULL | NULL |
+----+--------------+------+-------+
4 rows in set (0.00 sec)
I get a record and the id which is the primary key is empty. How is this possible?
I mean it is not NULL but a primary key is not supposed to be empty either right?
You defined your id field as a varchar, which is a dumb idea when you're using it to store integers. an empty field is NOT null. a zero-length string is still a valid string, and therefore a valid id value as far as your table is concerned. Try inserting ANOTHER blank string and you'll get a primary key violation:
INSERT INTO yourtable (id) VALUES (''); // will not work
The id field should be an int type. That'd disallow "empty" values.
primary keys are unique so if you alter the table, then the second row will attempt to add an empty value and fail. as a result, it will attempt the next possible value. If you want the first value not to be empty, you can set a default value.
It's not empty. It's probably an empty string. Note that the datatype is varchar(20).
Well, you didn't assign a value to the primary key field, so the default is NULL.
.
You want to modify the table so the primary key is auto_increment.
You can use a varchar as a foreign key related to another database table, but if you wish to use it as a numerical key, you should utilize a numerical data type such as int.
I know this doesn't answer the precise question regarding the primary key, but as your question does point out the fact you are also having issues parsing out the city and state from your location column, here's the query you would want to use (note you want an UPDATE to modify existing rows, not an INSERT which will add new rows rather than columns):
UPDATE my_contacts
SET
city = substr(location, 1, locate(',', location) - 1),
state = substr(location, locate(',', location) + 1);
For a preferences module I have "system defaults", and "user preferences".
If there is no personal/user preference stored, then use the system default values instead.
Here is my system preferences table:
mysql> desc rbl;
+-------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------------------+------+-----+---------+-------+
| id | varchar(3) | NO | PRI | | |
| rbl_url | varchar(100) | NO | | | |
| description | varchar(100) | NO | | | |
| is_default | tinyint(1) unsigned | YES | | 1 | |
+-------------+---------------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
Example data from system prefs:
mysql> select * from rbl;
+----+----------------------+------------------------------+------------+
| id | rbl_url | description | is_default |
+----+----------------------+------------------------------+------------+
| 1 | sbl-xbl.spamhaus.org | Spamhaus SBL-XBL | 1 |
| 2 | pbl.spamhaus.org | Spamhaus PBL | 1 |
| 3 | bl.spamcop.net | Spamcop Blacklist | 1 |
| 4 | rbl.example.com | Example RBL - not functional | 0 |
+----+----------------------+------------------------------+------------+
... and Query for system defaults:
mysql> SELECT rbl_url FROM rbl WHERE is_default='1';
+----------------------+
| rbl_url |
+----------------------+
| sbl-xbl.spamhaus.org |
| pbl.spamhaus.org |
| bl.spamcop.net |
+----------------------+
3 rows in set (0.01 sec)
So far so good.
OK. Now I need a user preferences table, and I came up with this:
mysql> desc rbl_pref;
+-----------+-----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-----------------------+------+-----+---------+----------------+
| id | mediumint(8) unsigned | NO | PRI | NULL | auto_increment |
| domain_id | mediumint(8) unsigned | NO | | NULL | |
| rbl_id | tinyint(1) unsigned | NO | | NULL | |
+-----------+-----------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
(FYI - A "user" is represented by "domain_id". )
Let's view the preferences of a specific user who has personalized preferences saved:
mysql> select * from rbl_pref where domain_id='2277';
+----+-----------+--------+
| id | domain_id | rbl_id |
+----+-----------+--------+
| 4 | 2277 | 1 |
| 5 | 2277 | 2 |
| 6 | 2277 | 4 |
+----+-----------+--------+
3 rows in set (0.00 sec)
... again, but in a simpler format:
mysql> SELECT rbl.rbl_url FROM rbl_pref,rbl
WHERE rbl_pref.rbl_id=rbl.id AND domain_id='2277';
+----------------------+
| rbl_url |
+----------------------+
| sbl-xbl.spamhaus.org |
| pbl.spamhaus.org |
| rbl.example.com |
+----------------------+
3 rows in set (0.00 sec)
.. so far so good. If a user has stored a preference, a result is found.
The problem example now is, user 1999 has no custom preferences.
In place of the "Empty set" result, I want the system defaults.
mysql> SELECT rbl.rbl_url FROM rbl_pref,rbl
WHERE rbl_pref.rbl_id=rbl.id AND domain_id='1999';
Empty set (0.00 sec)
I was excited to find a very similar question:
mysql if row doesn't exist, grab default value
However after a couple of days trial and error and documentation review, I could not translate that answer over to here.
Like the above question, this must be done as a single MySQL query. I am not actually making this query from PHP, but from Exim macros (and it is a very picky language... best to feed it "one liners" as variable assignments, as I try to do here.. )
UPDATE: Tried one type of a UNION query suggested by #Biff McGriff, below. The table did not display in my comment reply, so here it is again:
mysql> SELECT rbl.rbl_url FROM rbl_pref,rbl
WHERE rbl_pref.rbl_id=rbl.id AND domain_id='2277'
UNION SELECT rbl_url FROM rbl WHERE is_default='1';
+----------------------+
| rbl_url |
+----------------------+
| sbl-xbl.spamhaus.org |
| pbl.spamhaus.org |
| rbl.example.com |
| bl.spamcop.net |
+----------------------+
4 rows in set (0.00 sec)
As you can see above, user 2277 did not opt in to rbl_id 3 (bl.spamcop.net), but that's showing up anyways.
What my UNION query seems to be doing is combining the result set. So user_pref acts as "in addition to" global defaults, and I was assuming/expecting I would get a result set matching either half of the query.
So my question now is, is it better (or possible, how) to solve this as "either result set" (either subquery on either side of the UNION)? OR do I really need a new field on rbl_pref, called for example "enabled". The latter seems to be more correct - that I need something in rbl_pref to explicitly designate opt-in or opt-out (other than the implicit "that pref is not here - no rbl_id=3 - in the over ridden user result SET")
UPDATE: All set, thanks #Imre L, and everyone else. I learned something through this example.
You should be able to use a left join and then coalesce the user's field with the default field.
NOTE: you have to enter the domain_id in two places.
SELECT rbl.rbl_url FROM rbl
JOIN rbl_pref ON rbl_pref.rbl_id=rbl.id AND domain_id=2277
UNION
SELECT rbl.rbl_url FROM rbl
WHERE rbl.is_default
AND NOT EXISTS (SELECT 1 FROM rbl_pref WHERE domain_id=2277 LIMIT 1)
;
Now one or the other side of UNION will be optimized away with impossible where
You also should not use varchar(3) for rbl.id but some sort of integer
and preferable same type as rbl_pref.rbl_id for which tinyint is too tiny
and when you compare integers fields in sql code domain_id='2277' you should not use ' or " around constants integers.
You can get away whith it mostly but sometimes it may confuse mysql optimizer.
Also for optimal performance and consistency i suggest you the add the index:
ALTER TABLE rbl_pref
ADD UNIQUE INDEX ux_domain_rbl (domain_id, rbl_id);