Hey all, I am looking for a way to query my database table only once in order to add an item and also to check what last item count was so that i can use the next number.
strSQL = "SELECT * FROM productr"
After that code above, i add a few product values to a record like so:
ID | Product | Price | Description | Qty | DateSold | gcCode
--------------------------------------------------------------------------
5 | The Name 1 | 5.22 | Description 1 | 2 | 09/15/10 | na
6 | The Name 2 | 15.55 | Description 2 | 1 | 09/15/10 | 05648755
7 | The Name 3 | 1.10 | Description 3 | 1 | 09/15/10 | na
8 | The Name 4 | 0.24 | Description 4 | 21 | 09/15/10 | 658140
i need to count how many times it sees gcCode <> 'na' so that i can add a 1 so it will be unique. Currently i do not know how to do this without opening another database inside this one and doing something like this:
strSQL2 = "SELECT COUNT(gcCode) as gcCount FROM productr WHERE gcCode <> 'na'
But like i said above, i do not want to have to open another database query just to get a count.
Any help would be great! Thanks! :o)
There's no need to do everything in one query. If you're using InnoDB as a storage engine, you could wrap your COUNT query and your INSERT command in a single transaction to guarantee atomicity.
In addition, you should probably use NULL instead of na for fields with unknown or missing values.
They're two queries; one is a subset of the other which means getting what you want in a single query will be a hack I don't recommend:
SELECT p.*,
(SELECT COUNT(*)
FROM PRODUCTR
WHERE gccode != 'na') AS gcCount
FROM PRODUCTR p
This will return all the rows, as it did previously. But it will include an additional column, repeating the gcCount value for every row returned. It works, but it's redundant data...
Related
I have a table from which I would like to extract all of the column values for all rows. However, the query needs to be able to skip the first entry for each unique value of id_customer. It can be assumed that there will always be at least two rows containing the same id_customer.
I've compiled some sample data which can be found here: http://sqlfiddle.com/#!9/c85b73/1
The results I would like to achieve are something like this:
id_customer | id_cart | date
----------- | ------- | -------------------
1 | 102 | 2017-11-12 12:41:16
2 | 104 | 2015-09-04 17:23:54
2 | 105 | 2014-06-05 02:43:42
3 | 107 | 2011-12-01 11:32:21
Please let me know if any more information/better explanation is required, I expect it's quiet a niche solution.
One method is:
select c.*
from carts c
where c.date > (select min(c2.date) from carts c2 where c2.id_customer = c.id_customer);
If your data is large, you want an index on carts(id_customer, date).
I have two tables
one as td_job which has these structure
|---------|-----------|---------------|----------------|
| job_id | job_title | job_skill | job_desc |
|------------------------------------------------------|
| 1 | Job 1 | 1,2 | |
|------------------------------------------------------|
| 2 | Job 2 | 1,3 | |
|------------------------------------------------------|
The other Table is td_skill which is this one
|---------|-----------|--------------|
|skill_id |skill_title| skill_slug |
|---------------------|--------------|
| 1 | PHP | 1-PHP |
|---------------------|--------------|
| 2 | JQuery | 2-JQuery |
|---------------------|--------------|
now the job_skill in td_job is actualy the list of skill_id from td_skill
that means the job_id 1 has two skills associated with it, skill_id 1 and skill_id 2
Now I am writing a query which is this one
SELECT * FROM td_job,td_skill
WHERE td_skill.skill_id IN (SELECT td_job.job_skill FROM td_job)
AND td_skill.skill_slug LIKE '%$job_param%'
Now when the $job_param is PHP it returns one row, but if $job_param is JQuery it returns empty row.
I want to know where is the error.
The error is that you are storing a list of id's in a column rather than in an association/junction table. You should have another table, JobSkills with one row per job/skill combination.
The second and third problems are that you don't seem to understand how joins work nor how in with a subquery works. In any case, the query that you seem to want is more like:
SELECT *
FROM td_job j join
td_skill s
on find_in_set(s.skill_id, j.job_skill) > 0 and
s.skill_slug LIKE '%$job_param%';
Very bad database design. You should fix that if you can.
I have a mysql user table that holds user data like that:
userid | title | content
----------------------------------
1 | about | I am from ...
1 | location | Norway
1 | name | Mark
1 | website |
2 | about |
2 | location |
2 | name |
2 | website |
3 | ...
As you see the content is empty for userid 2, and also for many more users in the table.
My goal is to select only the userids that have at least 3 fields filled. All others should be ignored.
As my mysql knowledge is still weak I could not find a solution for this. I only found the opposite and just with count: Find the count of EMPTY or NULL columns in a MySQL table
What is the magic mysql query? Any help appreciated, thank you.
You would use aggregation and a having clause for this:
select u.userId
from users u
where content > '' and content is not null
group by u.userId
having count(*) >= 3;
I added the non-blank check as well as the null check. The null check is redundant, but it makes the intention clearer.
Background
I have a web application which must remove entries from other tables, filtered through a selection of 'tielists' from table 1 -> item_table 1, table 2, table 3.... now basically my result set is going to be filthy big unless I use a filter statement from another table, using a user_id... so can someone please help me structure my statement as needed? TY!
Tables
cars_belonging_to_user
-----------------------------
ID | user_id | make | model
----------------------------
1 | 1 | Toyota | Camry
2 | 1 |Infinity| Q55
3 | 1 | DMC | DeLorean
4 | 2 | Acura | RSX
Okay, Now the three 'tielists'
name:tielist_one
----------------------------
id | id_of_car | id_x | id_y|
1 | 1 | 12 | 22 |
2 | 2 | 23 | 32 |
-----------------------------
name:tielist_two
-------------------------------
id | id_of_car | id_x | id_z|
1 | 3 | 32 | 22 |
-----------------------------
name: tielist_three
id | id_of_car | id_x | id_a|
1 | 4 | 45 | 2 |
------------------------------
Result Set and Code
echo name_of_tielist_table
// I can structure if statements to echo result sets based upon the name
// Future Methodology: if car_id is in tielist_one, delete id_x from x_table, delete id_y from y_table...
// My output should be a double select base:
--SELECT * tielists from WHERE car_id is 1... output name of tielist... then
--SELECT * from specific_tielist where car_id is 1.....delete x_table, delete y_table...
Considering the list will be massive, and the tielist equally long, I must filter the results where car_id(id) = $variable && user_id = $id....
Side Notes
Only one car id will appear once in any single tielist..
This select statement MUST be filtered with user_id = $variable... (and remember, i'm looking for which car id too)
I MUST HAVE THE NAME of the tielist it comes from able to be echo'd into a variable...
I will only be looking for one single id_of_car at any given time, because this select will be contained in a foreach loop.
I was thinking a union all items would do the trick to select the row, but how can I get the name of the tielist the row is in, and how can the filter be used from the user_id row
If you want performance, I would suggest left outer join instead of union all. This will allow the query to make efficient use of indexes for your purpose.
Based on what you say, a car is in exactly one of the lists. This is important for this method to work. Here is the SQL:
select cu.*,
coalesce(tl1.id_x, tl2.id_x, tl3.id_x) as id_x,
tl1.y, tl2.idz, tl3.id_a,
(case when tl1.id is not null then 'One'
when tl2.id is not null then 'Two'
when tl3.id is not null then 'Three'
end) as TieList
from Cars_Belonging_To_User cu left ouer join
TieList_One tl1
on cu.id_of_car = tl1.id_of_car left outer join
TieList_Two tl2
on cu.id_of_car = tl2.id_of_car left outer join
TieList_Three tl3
on cu.id_of_car = tl3.id_of_car;
You can then add a where clause to filter as you need.
If you have an index on id_of_car for each tielist table, then the performance should be quite good. If the where clause uses an index on the first table, then the joins and where should all be using indexes, and the query will be quite fast.
I've got a table in MySQL that looks roughly like:
value | count
-------------
Fred | 7
FRED | 1
Roger | 3
roger | 1
That is, it was created with string ops outside of MySQL, so the values are case- and trailing-whitespace-sensitive.
I want it to look like:
value | count
-------------
Fred | 8
Roger | 4
That is, managed by MySQL, with value a primary key. It's not important which one (of "Fred" or "FRED") is kept.
I know how to do this in code. I also know how to generate a list of problem values (with a self-join). But I'd like to come up with a SQL update/delete to migrate my table, and I can't think of anything.
If I knew that no pair of records had variants of one value, with the same count (like ("Fred",4) and ("FRED",4)), then I think I can do it with a self-join to copy the counts, and then an update to remove the zeros. But I have no such guarantee.
Is there something simple I'm missing, or is this one of those cases where you just write a short function outside of the database?
Thanks!
As an example of how to obtain the results you are looking for with a SQL query alone:
SELECT UPPER(value) AS name, SUM(count) AS qty FROM table GROUP BY name;
If you make a new table to hold the correct values, you INSERT the above query to populate the new table as so:
INSERT INTO newtable (SELECT UPPER(value) AS name, SUM(count) AS qty FROM table GROUP BY name);
Strangely, MySQL seems to do this for you. I just tested this in MySQL 5.1.47:
create table c (value varchar(10), count int);
insert into c values ('Fred',7), ('FRED',1), ('Roger',3), ('roger',1);
select * from c;
+-------+-------+
| value | count |
+-------+-------+
| Fred | 7 |
| FRED | 1 |
| Roger | 3 |
| roger | 1 |
+-------+-------+
select value, sum(count) from c group by value;
+-------+------------+
| value | sum(count) |
+-------+------------+
| Fred | 8 |
| Roger | 4 |
+-------+------------+
I was surprised to see MySQL transform the strings like that, and I'm not sure I can explain why it did that. I was expecting to have to get four distinct rows, and to have to use some string functions to map the values to a canonical form.