I'm trying to make a new table from the inner join results of three other tables (t1, t2, t3)
INSERT INTO new_table
SELECT
t1.application_id,
t1.text,
t2.names,
t2.title,
t3.org_name, t3.project_start, t3.project_end, t3.keywords
FROM t1
INNER JOIN t2 ON t1.application_id = t2.application_id
INNER JOIN t3 ON t1.application_id = t3.application_id;
but keep getting a ER_DUP_ENTRY: Duplicate entry '9481301' for key 'PRIMARY'error. Each table should have id as a primary key so I'm confused why this is happening - how would one find and delete all the duplicates?
I bet your new_table is defined with an AUTOINCREMENT primary key.
To make your INSERT work correctly you'll need to let MySQL set that value rather than providing it from your SELECT. Something like this may work for you.
INSERT INTO new_table
(text, names, title, org_name, project_start, project_end, keywords)
SELECT
t1.text,
t2.names,
t2.title,
t3.org_name, t3.project_start, t3.project_end, t3.keywords
FROM t1
INNER JOIN t2 ON t1.application_id = t2.application_id
INNER JOIN t3 ON t1.application_id = t3.application_id;
You do this by leaving the id value out of your SELECT, and by enumerating the columns you want to INSERT.
(This is a guess: you didn't show us your table definition.)
Related
I have an issue with select command from 2 tables.
So I have table1 with:
table1_id = int pk;
table1_name;
table1_surname;
table1_age;
table1_address;
table1_city;
And table2 with:
table2_id int pk
table1_id int fk references table1.table1_id;
table3_id;
table2_description;
When I write the following select statement, I get ambigous column name table1.table1_name error:
SELECT table2.table2_id, table2.table1_id, table1.table1_name, table2.table2_description
from table1,
table2 inner join
table1
on table2.table1_id = table1.table1_id;
Honestly I do not understand what is wrong about it?
If i understood correctly, you have problem in below line
from table1, table2
In the above code you are using a CROSS JOIN between table2 and table1 which is not required in your case.
Change your query like following.
SELECT table2.table2_id, table2.table1_id, table1.table1_name, table2.table2_description
from table2
inner join table1 on table2.table1_id = table1.table1_id;
Never use commas in the FROM clause. Always use proper, explicit JOIN syntax:
select t2.table2_id, t2.table1_id, t1.table1_name, t2.table2_description
from table1 t1 join
table2 t2
on t2.table1_id = t1.table1_id;
The problem with your query is that you have two references to table1 because of the comma. You have mentioned the table twice. Hence, when you reference the column, the engine doesn't know what you are referring to. Your version is equivalent to:
from table1 cross join
table2 join
table1
on table2.table1_id = table1.table1_id
table1 appears twice, so any reference to it is ambiguous.
You will notice that I also added table aliases to the query. Table aliases make the query easier to write and to read.
Remove table1, just after from ( mixed old type "comma" and modern join syntaxes)
Use like the following :
SELECT t2.table2_id, t2.table1_id, t1.table1_name, t2.table2_description
FROM table2 t2 INNER JOIN table1 t1 ON ( t2.table1_id = t1.table1_id ) ;
I've two tables, table1 contains 22780 rows. Now I left join table1 with table2 (which doesn't contain any duplicates) and I get 23588 rows.
SELECT * FROM Table1
left join Tabelle6 ON CAST(Table1.Customer AS Int) = table2.Customer
Why do I get more rows now? I only need every row from table1 once.
Edit: found my issue, table 2 does contain duplicates. But is there any way to join every row only once and ignore any further matches?
As the comment suggests, the easiest way to handle this would probably be to do SELECT DISTINCT to remove duplicates from your result set:
SELECT DISTINCT
t1.col1,
t1.col2,
t1.Customer,
...
FROM Table1 t1
LEFT JOIN Table2 t2
ON CAST(t1.Customer AS Int) = t2.Customer
But there is another option here. We could also join to a subquery which removes duplicate customers. This would ensure that no record from the first table gets duplicated from matching to more than one record in the second table.
SELECT *
FROM Table1 t1
LEFT JOIN
(
SELECT DISTINCT Customer
FROM Table2
) t2
ON CAST(t1.Customer AS Int) = t2.Customer
I am having two tables, the structure is given below
Table 1
schid
name
cost
type
Table 2
schid
details
oldcost
I am unable to write a query to display records from table 2 of let suppose type A OR B (Here as you can see type field is in table 1), Here one more thing to add is that schid is not a primary key, The query which i am executing is retrieving more records than expected, I think due to join, Can i execute it without using join
SELECT *
FROM Table1
JOIN Table2 ON Table1.schid=Table2.schid
WHERE Table1.type='A'
OR Table1.type='B'
This would help:
SELECT t2.schid, t2.details, t2.oldcost
FROM Table2 t2
JOIN Table1 t1
ON t1.schid = t2.schid
WHERE t1.type IN ('A', 'B');
This should retrieve only the table 2 records which match the criteria.
SELECT t2.*
FROM Table2 t2
JOIN Table1 t1 ON t1.schid = t2.schid
WHERE t1.type = 'A'
OR t1.type = 'B';
SELECT t2.*
FROM `Table2` t2
JOIN `Table1` t1 ON t2.`schid`=t1.`schid`
WHERE t1.`type` IN ('A','B');
I have two tables with users and I want to select the users from the first table which do not exist in the second. Can you help me?
When I use the code
Select t1.user_name From t1 Inner Join t2 On t1.user_name != t2.user_name;
I get all the users many times (actually as the number of the users - 1).
Use a LEFT JOIN instead like
Select t1.user_name From t1 left join t2
On t1.user_name = t2.user_name
where t2.user_name is null;
You can use EXISTS like this
SELECT t1.user_name FROM t1 WHERE NOT EXISTS (SELECT 1 FROM t2 WHERE t1.id = t2.id)
This example assumes that you have some sort of ID on the tables that represents the primary key and foreign key.
Not sure how are your tables designed, but having the same info (user_name) in more than one table is considered as duplication of data. To fix this, you should read about Database normalization
How do I INNER JOIN a table that contains 2 foreign keys as its primary keys?
CREATE TABLE table1 (table1ID CHAR(4));
CREATE TABLE MEM_INSTR (table2ID CHAR(4));
CREATE TABLE table3 (table1ID CHAR(4), table2ID CHAR(4));
Assuming you want to just join everything together as keys suggest...
SELECT *
FROM table1
INNER JOIN table3 on table3.table1ID = table1.table1ID
INNER JOIN MEM_INSTR on MEM_INSTR.table2ID = table3.table2ID
But let's say that you have this scenario.
CREATE TABLE Table1 (
Table1ID NUMBER,
Generation NUMBER,
...
);
CREATE TABLE Table2 (
Table2ID NUMBER,
Table1ID NUMBER,
Table1Generation NUMBER,
...
);
Let's say for argument's sake that Table1 can have multiple records with the same Table1ID, and Generation is used as a secondary key. And you need to join a Table2 record to the correct single Table1 record. You can expand the ON clause the same way you would expand a WHERE clause.
SELECT *
FROM table1 t1
INNER JOIN table2 t2
ON t2.table1id = t1.table1id
AND t2.table1generation = t1.generation
You join it like you usually do, nothing really special about that. So you go something like this:
SELECT ...
FROM table1
INNER JOIN table3 ON table3.table1ID = table1.table1ID
INNER JOIN MEM_INSTR ON MEM_INSTR.table2ID = table3.table2ID