I have two tables. t1 contains business info:
t1
id | busName | busPhone
t2 contains business hours
t2
id | busId | open | close
Where t1.id = t2.busId
I need to create a query and loop through it and if t2 does not have corresponding records, select those in order to add data. Clearly the query below is incorrect...
SELECT t1.id
FROM t1
LEFT JOIN t2 ON (t1.id = t2.busId)
WHERE t2.id != ''
This should be your query:
SELECT DISTINCT(t1.id)
t1 LEFT JOIN t2 ON (t1.id = t2.busId)
WHERE t2.busId IS NULL
select id from t1 where id not in (select busId from t2)
Related
Here are 2 tables.
Table 1
id value
1 3
2 2
3 3
4 1
5 4
6 3
Table 2
id
1
3
4
How do I get the ids that are in Table 2 which have the max value in Table 1?
Output:
id
1
3
I already tried the following to get the max value, but I cannot figure out how to use it in a single query to get the matching rows. Because I think I need to select from the same table I just inner joined.
select max(table1.value)
from table2
inner join table1 on table1.id = table2.id;
Here is one method:
select t2.id
from (select t2.*, rank() over (order by value desc) as seqnum
from table2 t2 join
table1 t1
on t2.id = t1.id
) t
where seqnum = 1;
Or, an alternative that puts all the ids on one row:
select group_concat(t2.id) as ids
from table2 t2 join
table1 t1
on t2.id = t1.id
group by t1.value
order by t1.value desc
limit 1;
You have a couple of options available without using window functions:
You can use a WHERE clause to select only id values that have a value equal to the MAX(value) from your query and an id that is in Table2:
SELECT t1.id
FROM Table1 t1
WHERE value = (
SELECT MAX(t1.value)
FROM Table2 t2
JOIN Table1 t1 ON t1.id = t2.id
)
AND id IN (SELECT id FROM Table2)
You can JOIN your query to Table1 and Table2 again, matching the value in Table1 and the id in Table2:
SELECT t1.id
FROM (
SELECT MAX(t1.value) AS max_value
FROM Table2 t2
JOIN Table1 t1 ON t1.id = t2.id
) t
JOIN Table1 t1 ON t1.value = t.max_value
JOIN Table2 t2 ON t2.id = t1.id
In both cases the output is
id
1
3
Demo on SQLFiddle
Too low to comment but from the SQL statement you gave, you just need to add the tableid in your select parameters.
select table2.id, max(table1.value)
from table2
inner join table1 on table1.id = table2.id;
I have some SQL code that returns me some data from DB
SELECT t1.id as id, title, description FROM table1 t1
JOIN table2 t2 ON t1.id = t2.t1_id
WHERE t2.t3_id IN( SELECT id FROM table3 WHERE parent_id IN ( SELECT id FROM table3 WHERE parent_id = 1)) GROUP BY t1.id
I have some problem with counting number of rows of result. I know that I have to write almost the same code but with COUNT but I have there A problem, my code doesn't return me a number of rows.
Just use the COUNT(*) function. Also, your subqueries can be converted to a JOIN (and your sub-subquery is redundant):
SELECT COUNT(*)
FROM table1 t1
JOIN table2 t2
ON t1.id = t2.t1_id
JOIN table3 t2
ON t3.id = t2.t3_id
WHERE t3.parent_id = 1
I have been using the following SQL:
SELECT DISTINCT NAME
FROM Events t1
LEFT JOIN UserHistory t2 ON t1.Name = t2.Event
WHERE t2.Event IS NULL
To select all rows from table 1 where table 2 is Null. This effectively filters out all my Table 1 data where Table 2 has data. However, I want to apply this only when a column in table 2 equals a certain value. Therefore I am looking to do a SELECT * FROM t2 WHERE t2.ID = 1 but am unsure how this fits into this query.
SELECT DISTINCT NAME
FROM Events t1
LEFT JOIN UserHistory t2 ON t1.Name = t2.Event and t2.certain_column = 1234
WHERE t2.Event IS NULL
Also you can try query with NOT EXISTS:
SELECT DISTINCT NAME
FROM Events t1
WHERE NOT EXISTS(SELECT * FROM UserHistory t2
WHERE t1.Name = t2.Event AND t2.ID = 1)
You need to add the predicate to the JOIN condition:
SELECT DISTINCT NAME
FROM Events t1
LEFT JOIN UserHistory t2 ON t1.Name = t2.Event AND t2.ID = 1
WHERE t2.Event IS NULL;
If you add it to the WHERE you effectively turn your outer join into an inner join, meaning no rows will be returned (since NULL = 1 evaluates to false)
Ok. I have some data in one table, that references on multiple occasions some data in another table.
Table1 - main client table
Table2 - user defined fields
Say I have a query that shows a client id from Table1 and all attached / used "used defined fields" from Table2
SELECT t1.Id, t2.udf
FROM Table1 t1
JOIN Table2 t2 ON t1.Id = t2.Index
WHERE t1.EndDate IS NULL AND
t1.Id = '1234.9876' AND
I would get the following for a result...
ID UDF
1234.9876 100
1234.9876 110
1234.9876 118
1234.9876 124
1234.9876 198
1234.9876 256
Now, say I wanted to query this same thing, and get ONLY the ID of the Client, but ONLY IF a value for t2.udf equaling '194' did not exist. So, I would simply get
ID
1234.9876
...as a result.
Make the join a LEFT join and filer where t2.Index is null
SELECT t1.Id
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.Id = t2.Index
AND t2.UDF = 194 -- has to be before where clause
WHERE t2.Index IS NULL
AND t1.EndDate IS NULL
AND t1.Id = '1234.9876' -- not sure if you want this part
Another way by using NOT EXISTS
SELECT t1.Id
FROM Table1 t1
WHERE NOT EXISTS (SELECT 1 FROM Table2 t2 WHERE t1.Id = t2.INDEX
AND t2.UDF = 194)
AND t1.EndDate IS NULL
AND t1.Id = '1234.9876'
See also JOINS
You can add AND t2.udf not in (select udf from table2 where udf <> '194').
But #SQLMenace solution is better
This should do it.
SELECT DISTINCT t1.Id
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.Id = t2.Index
WHERE t2.UDF NOT IN (194)
AND t2.Index IS NULL
Select DISTINCT gives you unique entries that satisfy the other conditions, and the first where clause
t2.UDF NOT IN (194)
Normall would return all the rows for the t1 where the t2.UDF is not 194, but it is limited by the Select Distinct to give you only distinct id's
Try the following:
SELECT t1.Id
FROM Table1 t1
JOIN Table2 t2 ON t1.Id = t2.Index
WHERE t1.EndDate IS NULL AND
t1.Id = '1234.9876' AND
t2.udf <> '194'
I have the 2 following tables t1, t2 with values,
t1 t2
1 4
2 2
3 3
Now I want to output
1
4
How can I get this output in select query ?
This will get you each item from t1 that is not present in t2, and each item in t2 that is not present in t1:
select t1.id from t1
left join t2 on t2.id = t1.id
where t2.id is null
union all
select t2.id from t2
left join t1 on t1.id = t2.id
where t1.id is null
(I have assumed that the field name in each table is named id just for the sake of being able to write a query against the tables.)
Another way would be:
select coalesce(t1.id, t2.id)
from t1
full outer join t2 on t2.id = t1.id
where t1.id is null or t2.id is null
Another way. Just COUNT them.
This works if the values are unique per table
SELECT
CombinedValue
FROM
(
SELECT t1 AS CombinedValue FROM t1
UNION ALL
SELECT t2 FROM t2
) foo
GROUP BY
CombinedValue
HAVING
COUNT(*) = 1
If not unique per table
SELECT
CombinedValue
FROM
(
SELECT DISTINCT t1 AS CombinedValue FROM t1
UNION ALL
SELECT DISTINCT t2 FROM t2
) foo
GROUP BY
CombinedValue
HAVING
COUNT(*) = 1
you can use Joins in MySql to proceed and to obtain result.
this will help you
http://www.techrepublic.com/article/sql-basics-query-multiple-tables/1050307