I need to insert identifiers (numbers) into a temporary table which satisfy several conditions.
I use insert into select structure.
One of the conditions is the next. There are tables received_posts_1(id,post_id), received_posts_2(id,post_id)...
Each selected identifier is part of a table name with received posts. I need to add an and part into the where clause of the next form.
and not exists(select 1 from CURRENT_RECEIVED_POSTS_TABLE where id = device_id and post_id = post_id_)
The insertion is in while cycle. The stop condition is a needed count of identifiers to be inserted.
Having multiple tables with the same structure is generally a sign of a poor database design. In general, it is much better to have a single table, with columns that distinguish what you are trying to do.
One approach is to create such a table using a view:
create view received_posts
select 1 as which, r.* from received_posts_1 r union all
select 2, r.* from received_posts_2 r union all
. . .;
You can then use this table in your query.
A more efficient method is to repeat the exists, with the right conditions:
not exists(select 1
from received_posts_1
where id = device_id and post_id = 1) and
not exists(select 1
from received_posts_2
where id = device_id and post_id = 2) and
. . .
As mentioned in the comments, you can use dynamic SQL if you know which post table you need for a particular invocation of the query.
Related
I read the previous posts but I couldn't find one that answered my question.
What would be the name of the table that is made by joining two tables? The reason why I need the name is because I would like to change the column name of the new table using the ALTER TABLE (Table name) RENAME COLUMN (A) to (B). If there is no specified name, how can I name the new table?
ex
SELECT
client_id
,last_name
FROM INDIVIDUAL_CLIENT
UNION ALL
SELECT
client_id
,bus_name
FROM BUSINESS_CLIENT;
I would like to rename the column to last_name/bus_name instead of last_name
In the case of a query what temporal table a query might create internally is not relevant, because you a making a query and getting data back, it doesn't stay in the database as a table, there is no such table. Unless we make it.
if You want TSQL to change a column name it would affect your union query and I base my answer on Your
'I would like to rename the column to last_name/bus_name instead of last_name'
And think this is what you're looking for. Please correct me if it isn't.
In generic SQL what we're doing is putting a label on both projections that are to be displayed in the same column
SELECT
client_id
,last_name [last_name/ bus_name]
FROM INDIVIDUAL_CLIENT
UNION ALL
SELECT
client_id
,bus_name [last_name/ bus_name]
FROM BUSINESS_CLIENT;
update, in MySQL notation uses AS and quotes instead of angle brackets
SELECT
client_id
,last_name as "last_name/ bus_name"
FROM INDIVIDUAL_CLIENT
UNION ALL
SELECT
client_id
,bus_name as "last_name/ bus_name"
FROM BUSINESS_CLIENT;
i'm working on an advanced search functionality on my website.
Basically data I'm working on is stored within two tables.
First table contains basic information about the product (1 row = 1 product so it's unique).
Table structure may look like this:
id, title, description
The second table contains more information about the product. The product may but don't have to have any rows here. However, one product may store in the second table a few rows. What's more - data in the second table should be used to the advanced search functionality. Table structure may looks like this:
id, item_id (from table 1), value_id (from another table), value
I want to select only these products (table 1) which has specified value_id (from column 2):
... WHERE table1.item_id = 5 AND table2.value_id = 1000
As I mentioned before - table 2 may but doesn't have to contains any rows connected by item_id with the table 1.
I've tried to use JOIN/LEFT JOIN function in SQL but in this case when the product has 3 rows in the table 2 - a query result returns 3 rows instead of 1 or 0 (if not found any results).
How can I handle that?
You want to select products. So select from the product table. You want to select only those for which exists a certain attribute. So create an approriate WHERE clause. As you want to look up data in another table, you could use EXISTS or IN.
select *
from items
where id in (select item_id from item_values where value_id = 1000);
I need some assistance with deleting data within an SQL Table if it matches data from another table.
There are two Tables
Table 1: DNC
Table 2: Call_Logs
Table 1 has only one column called phone_number.
Table 2 has multiple columns, but the main one that is important is also named phone_number.
Basically, I want to remove any numbers that are in Table 2 from Table 1, if they exist. Now, I don't want to delete every number from Table 1 if they exist in Table 2. What numbers I collect from Table 2 are based on some criteria.
To pull the data from Table 2 that I need to delete from Table 1, I use the following:
select phone_number from call_logs where call_date < 'DATE' and Status = 'DNC'
This query will give me a list of all phone numbers that I would want to remove from Table 1 if it exists.
EXAMPLE:
https://drive.google.com/file/d/0B4NE4ZDXd6steW5odWhBMDJSY1U/view
I am not sure how I would go about running the query in SQL. Any types would be appreciated it.
Looking to your sample in img
You could use a left join on table 2 (where table2.phone_number is null alias don't match)
delete from table1
left join table2 on table1.phone_number = table2.phone_number
where table2.phone_number is null
correlated subquery w/ an exists so it can early exit
The select 1 in the subquery is because we have to select a value but it doesn't matter what value that is. since the coloration (DNC.Phone_Number = CL.Phone_Number) is all we are after; along with your limits on call_log.
DELETE
FROM DNC
WHERE exists (SELECT 1
FROM Call_logs CL
WHERE CL.call_date < 'DATE'
and CL.Status = 'DNC'
and DNC.Phone_Number = CL.Phone_Number)
I have two tables, name tbl_siswa and tbl_tentor.
Both have an uniq id, in tbl_siswa called id_siswa and in tbl_tentor called tbl_tentor.
how to check if an input ID is from tbl_tentor or tbl_siswa in one query.
i can make this with PHP and mysql, but i need this only in mysql..
The fastest way is by a union:
select id_siswa as id
from tbl_siswa
where id_siswa = ?
union
select id_tentor
from tbl_tentor
where id_tentor = ?
Note that you will either get one row or no rows. Even if the id appears in both tables, you will only get one row because union removes duplicate rows.
I wanted to know if it was possible to make a select on a table that contains multiple field and join them in 1 result :
Example :
Table :
id
dayOne_City
dayTwo_City
dayThree_City
Result : one column that contains the rows of all the cities (Distinct).
2) Am i better to do a view if i have a lot of query to that specific list ?
3) should i do 3 select with union ?
Thank you
You should be fine with:
select dayOne_City from YourTable
UNION
select dayTwo_City from YourTable
UNION
select dayThree_City from YourTable
However, you should review your design to allow multiple cities per whatever-is-that-your-table stores. That is, create an actual many-to-many relationship by creating an intermediate table between YourTable and Cities.
select concat_ws(',', id, dayOne_city, dayTwo_city, dayThree_city, etc...) as allInOne
Details on the function used here. However, I should ask why you're doing this. By joining the fields together, you're destroy any chance of reliably extracting/separating the data again later. Only do this kind of "bulking" if you never plan on using separate portions of the data elsewhere based on the results of this query.