Consider following table:
| ID | COL1 |
| -- | ---- |
| 1 | xxx |
| 3 | xxx |
| 2 | xxx |
| 2 | xxx |
| 3 | xxx |
| 2 | xxx |
| 1 | xxx |
Im using command:
SELECT * FROM table WHERE ID=id
Problem is that table contains about 500 000 000 rows with 1000 different IDs and command is slow. My idea is somehow sort table by ID:
Modified table:
| ID | COL1 |
| -- | ---- |
| 1 | xxx |
| 1 | xxx |
| 2 | xxx |
| 2 | xxx |
| 2 | xxx |
| 3 | xxx |
| 3 | xxx |
With sorted table it should be faster. My question is how keep table sorted? OR is there any other way how make it faster?
Is that all there is to the table? That is, if there are only those 2 columns, then simply add
INDEX(id, col1)
That way you will get the optimized lookup you desire. It still won't be fast -- it needs to shovel about 500K rows to the client.
If the table is more complex than you have shown, my suggestion may be invalid. At least provide the complete SHOW CREATE TABLE. I may need to suggest a rearrangement of the PK.
Related
I have two MySQL tables called tasks and users. All I want to do is I don't want to display the tasks that is already done by a user in his panel. Suppose the task table has about 1000 entries and there are about 50000 users. Also the users and the tasks keep increasing.
One solution I can think of, 1st is creating a separate table of task x user size.
For example:
user table
+---------+--------+-------+
| user_id | fname | lname |
+---------+--------+-------+
| 1 | John | Smith |
| 2 | Steve | Mark |
+---------+--------+-------+
task table
+---------+-------------+---------------+
| task_id | task | task_duration |
+---------+-------------+---------------+
| 1 | Do task 1 | 1 hour |
| 2 | Do task 2 | 1 hour |
+---------+-------------+---------------+
Creating a separate table called display
+------------+---------+---------+
| display_id | task_id | user_id |
+------------+---------+---------+
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 2 | 1 |
| 4 | 2 | 2 |
+------------+---------+---------+
So only listed tasks will be shown to the particular user.
The problem is that This does not look like an efficient solution. How can I design table in this scenario in an efficient way. If not what are the other ways?
I'm trying to break up a SQL table that needs to take a users name and find the unique user ID's from up to 4 systems.
The data is currently like this:
| Name | User_ID |
-----------------
| A | 10 |
| A | 110 |
| A | 1500 |
| A | 4 |
| B | 20 |
| B | 100 |
| B | 2 |
| C | 10 |
I need to pivot it around the user's name to look like this (the id's don't need to be in numerical order as the SYS#_ID for each doesn't matter):
| Name | SYS1_ID | SYS2_ID | SYS3_ID | SYS4_ID |
------------------------------------------------
| A | 4 | 10 | 110 | 1500 |
| B | 2 | 20 | 100 | NULL |
| C | 10 | NULL | NULL | NULL |
This is the code I have tried on MySQL:
PIVOT(
COUNT(User_ID)
FOR Name
IN (SYS1_ID, SYS2_ID, SYS3_ID, SYS4_ID)
)
AS PivotedUsers
ORDER BY PivotedUsers.User_Name;
I'm unsure if PIVOT works on MySQL as I keep getting an error "PIVOT unknown". Is there a way to find the values that each user has and if they do not appear in the table already add them to the next column with a max of 4 values?
I am trying to run an MySQL query to copy over data from an old table (ps__product_review/rate) to a new table (ps_product_comment/grade) based on review ID (id_product_comment). But I am a bit lost on the SQL query, this is what I have but keep getting errors.
INSERT INTO ps_product_comment [(grade)]
SELECT rate
FROM ps__product_review
[WHERE ps__product_review.id_product_comment=ps_product_comment.id_product_comment];
Can anyone help write the correct query?
Edit:Essentially I am trying to populate the Grade column in the new table below.
Old table (ps__product_review)
+--------------------+----------+-----+
| id_product_comment | Comment | Rate|
+--------------------+----------+-----+
| 1 | Good | 2 |
| 2 | Great | 5 |
| 3 | OK | 3 |
| 4 | Brill | 4 |
| 5 | OK | 3 |
| 6 | Average | 2 |
| 7 | Bad | 1 |
+--------------------+----------+-----+
New Table (ps_product_comment)
+--------------------+----------+-------+
| id_product_comment | Comment | Grade |
+--------------------+----------+-------+
| 1 | Good | |
| 2 | Great | |
| 3 | OK | |
| 4 | Brill | |
| 5 | OK | |
| 6 | Average | |
| 7 | Bad | |
+--------------------+----------+-------+
If you want to update table with data from another table, use UPDATE with JOIN
UPDATE ps_product_comment
JOIN ps__product_review
ON ps__product_review.id_product_comment = ps_product_comment.id_product_comment
SET ps_product_comment.grade = ps__product_review.rate;
Remove the square brackets and I think you are missing the JOIN(since you are using that in your where clause):
INSERT INTO ps_product_comment (grade)
SELECT rate
FROM ps__product_review inner join ps_product_comment on
ps__product_review.id_product_comment=ps_product_comment.id_product_comment;
I want to create a webpage where user can organize things they collect. As everyone collects something else I want to have the users create their own datamodell (with strict limitations). If two people are collection the same "things" they can share a datastructure.
My idea was to give every collection an ID and all the tables belonging to that collection will have the ID as a prefix.
Table: Collections
ID | Collection
1 | Poststamps
2 | Barbie Dolls
Table: 1_Base
ID | StampValue | StampPic
....
Table: 2_Base
ID | EAN | Pic
....
Thus I would create many tables as each user could in theory create their own collection. I could also use only one very big table and a mapping table. Example:
Table: Colleactions
ID | Collection
1 | Poststamps
2 | Barbie Dolls
Table: Mapping
fkCollection | FieldName | Mapping
1 | DoubleField1 | StampValue
1 | BlobField1 | StampPic
2 | StringField1 | EAN
2 | BlobField1 | StampPic
Table: CollectionData
fkCollection | DoubleField1 | ... | DoubleField10 | StringField1 | ... | Stringfield10 | BlobField1 | ...
1 | 30 | | | | | | ... |
2 | | | | 21312412414 | | | ... |
Any other ideas?
Thanks for your help!
From what I can see, your second way of attempting this is going to be the easiest way... your queries will be ten fold simpler to handle, and you wouldn't need to programmably create tables on the fly... so my suggestion would be to modify your second idea slightly... Just to clarify something also, A blob will slow down the query speed so I am changing the block to hold the source link to the image instead.
TABLE: Collections
ID| Collection
1 | Poststamps
2 | Barbie Dolls
Table: CollectionData
fkCollection | DataType | VALUE | FieldName |
1 | Double | 30 | StampID |
1 | String | London | StampName |
1 | ImgSrc | ../loc | StampPic |
2 | String | Ken | BarbieName |
2 | ImgSrc | ../loc | BarbiePic |
I would like to create a view from a lookup table and actual data. I have two questions.
How would you accomplish this?
Should I try to do it this way?
Senerio
Table Name: steps
Table structure with values:
There are other columns hence the ( ... )
| id | Name | ... |
| 1 | Step One | ... |
| 2 | Step Two | ... |
Table Name: steps_completed
Table structure with values:
| user_id | steps_id |
| 1 | 1 |
| 2 | 1 |
| 2 | 2 |
Results Wanted
View Structure and Values wanted:
| user_id | step_one | step_two |
| 1 | 1 | 0 |
| 1 | 1 | 1 |
Thanks for your help.
Sounds like you need a cross tab query. The only way I've seen it done is via a stored procedure like this: Cross Tab Query