How con i find how many rows don't have an inner join relationship?
TABLE A
id | name | idpoints
TABLE B
id | point
any record on table A should have a relative record on table B
how can i find how many records on able A don't have a record on table B?
Use left join to join the tables and then take all records where the id in tableB is null
select count(*) from tableA left join tableB on idpoints = tableB.id where tableB.id is null
You can do the following
SELECT COUNT(1)
FROM TABLE_A A
LEFT JOIN TABLE_B B
ON B.ID = A.IDPOINTS
WHERE B.ID IS NULL
Related
I am trying to select all records in TABLEC and its equivalent value in TABLEA or TABLEB using right join. I am using MYSQL 5.5.47.
--Table data as follows
TABLEA TABLEB TABLEC
ID FNAME ID MNAME ID LNAME
0 ANOOP 0 N 0 SINGH
1 BIMA 2 SITA 3 RAJ
4 CIMI 4 B 5 KUMAR
6 RAVI 5 A 6 D
--Using below query and trying to select all records in TABLEC and its equivalent value in TABLEA or TABLEB
SELECT A.FNAME, B.MNAME, C.LNAME
FROM TABLEA AS A
RIGHT JOIN TABLEB AS B ON A.ID = B.ID
RIGHT JOIN TABLEC AS C ON C.ID = B.ID
--I am getting the following result
ANOOP N SINGH
NULL NULL RAJ
NULL A KUMAR
***NULL*** NULL D
The highlighted value doesn’t show the value as 'RAVI' instead it shows NULL in MYSQL 5.5.47. I tried to modify the '=' condition in second join related to C & A but still no luck. What am I doing wrong here? How do I get the value 'RAVI' in place of NULL? Any suggestion would be highly helpful.
DROP TABLE IF EXISTS table_a;
DROP TABLE IF EXISTS table_b;
DROP TABLE IF EXISTS table_c;
CREATE TABLE table_a
(id INT NOT NULL PRIMARY KEY
,fname VARCHAR(12) NULL
);
INSERT INTO table_a VALUES
(0,'ANOOP'),
(1,'BIMA'),
(4,'CIMI'),
(6,'RAVI');
CREATE TABLE table_b
(id INT NOT NULL PRIMARY KEY
,mname VARCHAR(12) NULL
);
INSERT INTO table_b VALUES
(0,'N'),
(2,'SITA'),
(4,'B'),
(5,'A');
CREATE TABLE table_c
(id INT NOT NULL PRIMARY KEY
,lname VARCHAR(12) NULL
);
INSERT INTO table_c VALUES
(0,'SINGH'),
(3,'RAJ'),
(5,'KUMAR'),
(6,'D');
SELECT a.fname
, b.mname
, c.lname
FROM table_c c
LEFT
JOIN table_a a
ON a.id = c.id
LEFT
JOIN table_b b
ON b.id = c.id;
+-------+-------+-------+
| fname | mname | lname |
+-------+-------+-------+
| ANOOP | N | SINGH |
| NULL | NULL | RAJ |
| NULL | A | KUMAR |
| RAVI | NULL | D |
+-------+-------+-------+
4 rows in set (0.02 sec)
You are trying to select all records in TABLEC and its equivalent value in TABLEA or TABLEB using right join. So Table A and B is joined to Table c records. So we need to use Left join(you will get all records of Table C and common records of Table A and B). More info please ref this link
SELECT
ifnull(A.FNAME,""),
ifnull(B.MNAME,""),
ifnull(C.LNAME,"")
FROM
TABLEA AS A
LEFT JOIN
TABLEB AS B
ON
A.ID = B.ID
LEFT JOIN
TABLEC AS C
ON
C.ID = B.ID
The problem is you don't have a table that contains all the ids. So you have to make one. Then you can join from that.
Get all the ids with this query
SELECT ID FROM TABLEA
UNION
SELECT ID FROM TABLEB
UNION
SELECT ID FROM TABLEC
Now we can use this query/table of ids to join the others
SELECT A.FNAME, B.MNAME, C.LNAME
FROM (
SELECT ID FROM TABLEA
UNION
SELECT ID FROM TABLEB
UNION
SELECT ID FROM TABLEC
) I
LEFT JOIN TABLEA A ON I.ID = A.ID
LEFT JOIN TABLEB B ON I.ID = B.ID
LEFT JOIN TABLEC C ON I.ID = C.ID
Of course if you had another table (TABLEID) that had a list of all IDs you could use that instead of the sub-query above. It might be your model has such a table, but we won't know unless you tell us.
As you said "select all records in TABLEC and its equivalent value in TABLEA or TABLEB", so you need to join the C with A and C with B. So your need to update your query as :
SELECT A.FNAME, B.MNAME, C.LNAME
FROM TABLEC AS C RIGHT JOIN TABLEB AS B
ON B.ID = C.ID
RIGHT JOIN TABLEA AS A
ON C.ID = A.ID
If you want all the record that exist in A, B and C. The NULL value will shown for the record which doesn't have the value,
SELECT A.FNAME, B.MNAME, C.LNAME
FROM (
TABLEA AS A
LEFT JOIN TABLEB AS B ON B.ID = A.ID
)
RIGHT JOIN TABLEC AS C ON ( C.ID = B.ID
OR B.ID = NULL
OR A.ID = C.ID )
WHERE 1
Use this works perfectly
SELECT A.FNAME, B.MNAME, C.LNAME
FROM TABLEC AS C
LEFT JOIN TABLEA AS A ON (A.ID = C.ID)
LEFT JOIN TABLEB AS B ON (B.ID = C.ID)
I have two tables. Primary key from table A is primary key in table B with another column.
So structure is like this.
Table A
id - PRIMARY
total_amount
Table B
id - PRIMARY
another_id PRIMARY
status
So i can have id from table A appear multiple times in table B.
My problem is that this query
SELECT IFNULL(SUM(total_amount), 0) AS amount
FROM tableA AS a
INNER JOIN tableB AS b
ON a.id = b.id
WHERE a.id = 10
AND status <> 'UNKNOWN'
sometimes returns more in amount the it should.
If total_amount on id 10 is 2, and that same id 10 repeats in table b three times my amount will be 6 instead of 2.
Is there a way I can avoid that. Some other way to write this query.
Thank you.
Use exists instead:
SELECT IFNULL(SUM(total_amount), 0) AS amount
FROM tableA a
WHERE EXISTS (SELECT 1
FROM tableB AS b
WHERE a.id = b.id AND b.status <> 'UNKNOWN'
);
DISTINCT the list of ids returned from tableB
SELECT
IFNULL(SUM(total_amount), 0) AS amount
FROM
tableA AS a INNER JOIN (SELECT DISTINCT id FROM tableB WHERE [status] <> 'UNKNOWN') AS b ON a.id = b.id
WHERE
a.id = 10
here is my problem:
I have two tables. Every entry of table A has several entries in table B matched over an ID. I now want to get all entries of table A with one data entry of table B - the one with the highest ID in this table.
Table A has an ID
Table B has an own ID and ID_OF_TABLE_A (for the relation between both)
Table A has one to many relation to Table B. I want all Entries of Table A, matched with the one with the highest ID out of B. Is there any way to realize this in an SQL Statement? I tried all kinds of joins since I need the information of that matched entry in the outcome of the select.
How about
SELECT *
FROM tableA a
INNER JOIN tableB b ON a.ID = b.ID_OF_TABLE_A
WHERE b.ID = (SELECT MAX(ID) FROM tableB c WHERE b.ID = c.ID)
Try this:
SELECT a.*, b.*
FROM tableA a
LEFT OUTER JOIN (SELECT b.*
FROM tableB b
INNER JOIN (SELECT ID_OF_TABLE_A, MAX(ID) bID
FROM tableB
GROUP BY ID_OF_TABLE_A
) c ON b.ID_OF_TABLE_A = c.ID_OF_TABLE_A AND b.ID = c.bID
) AS b ON a.ID = b.ID_OF_TABLE_A;
You can use an inline view where you filter the rows you need from table b with the help of the grouping clause and max function like so:
select a.*, b.*
from a
join (
select max(id) as id_b_max, id_a
from b
group by id_a
) b
on a.id = b.id_a;
Tested with:
create table a(id int);
create table b(id int, id_a int);
insert a values (1);
insert b values(1, 1);
insert b values(2, 1);
insert b values(3, 1);
select a.id, max(b.id)
from table_a a join table_b b on a.id = b.table_a_id
group by a.id
This should work. prefilter out the max id of the ID_OF_TABLE_A. and then join on that id.
SELECT A.*, B.*
FROM A
INNER JOIN ( SELECT max( ID ) AS id, ID_OF_TABLE_A
FROM B
GROUP BY ID_OF_TABLE_A) AS grp_b
ON grp_b.ID_OF_TABLE_A = a.ID
INNER JOIN B ON b.ID = grp_b.id
there is three table
table a
table b
table c
and my query is :
select a.title,a.id,b.title
from table a
case when a.type=1 then
inner join table a.id=tableb.id end
case when a.type=2 then inner join table a.id=table c.id
But this query doesnt work.Can somebody helpe the right way to fetch or execute this type of query
You cannot use case in the from clause. To achieve this you could use UNION ALL. For instance:
select a.title,a.id,b.title
from table a inner join table b on a.id=b.id
where a.type=1
UNION ALL
select a.title,a.id,c.title
from table a inner join table c on a.id=c.id
where a.type=2
You cannot do something like "if this is 1 then join other table than if it is 2", you must join both and select accordingly:
SELECT
a.title,
a.id,
IF (tableb.title IS NOT NULL, tableb.title, tablec.title),
CASE a.type
WHEN 1 THEN tableb.id
WHEN 2 THEN tablec.id
END
FROM table a
LEFT JOIN tableb ON tablea.id = tableb.id
LEFT JOIN tablec ON tablea.id = tablec.id
I have 2 table
Columns inside table_A : data, id_A, id_B, status
Columns inside table_B : id, username
I want to display username from table_B reference from columns inside table_A (id_A & id_B) and make the alias id_A as User_1 and id_B as User_2
I has been working with INNER JOIN but it still make me confused
Can you try this...
SELECT a.username as User_1, b.username as User_2 FROM
table_A t
JOIN table_B b on b.id = t.id_B
JOIN table_B a ON a.id = t.id_A