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.
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 have two tables. The first is named master_list. It has these fields: master_id, item_id, name, img, item_code, and length. My second table is named types_join. It has these fields: master_id and type_id. (There is a third table, but it is not being used in the queries. It is more for reference.) I need to be able to combine these two tables so that I can sift the results to only show certain ones but part of the information to sift is on one table and the other part is on the other one. I don't want duplicate answers.
For example say I only want items that have a type_id of 3 and a length of 18.
When I use
SELECT * FROM master_list LEFT JOIN types_join ON master_list.master_id=types_join.master_id WHERE types_join.type_id = 3 AND master_list.length = 18"
it finds the same thing twice.
How can I query this so I won't get duplicate answers?
Here are the samples from my tables and the result I am getting.
This is what I get with an INNER JOIN:
BTW, master_id and name both only have unique information on the master_list table. However, the types_join table does use the master_id multiple times later on, but not for Lye. That is why I know it is duplicating information.
If you want unique rows from master_list, use exists:
SELECT ml.*
FROM master_list ml
WHERE ml.length = 18 AND
EXISTS (SELECT 1
FROM types_join tj
WHERE ml.master_id = tj.master_id AND tj.type_id = 3
);
Any duplicates you get will be duplicates in master_list. If you want to remove them, you need to provide more information -- I would recommend a new question.
Thank you for the data. But as you can see enter link description here, there is nothing wrong with your query.
Have you tried create an unique index over master_id, just to make sure that you do not have duplicated rows?
CREATE UNIQUE INDEX MyMasterUnique
ON master_list(master_id);
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 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.
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.