I have one table:
id | parent_id | name
1 | NULL | audi
2 | 1 | a5
3 | 1 | a6
4 | NULL | opel
5 | 4 | astra
6 | 4 | vectra
I want get name of record and name of record's parent.
One example is to fetch the name for id=5 and its parent name.
id | name | parent_name
5 | astra | opel
What would be SQL query for this?
My query:
SELECT name, parent_id FROM `cats` WHERE `id` = 5 OR `id` =
cats.parent_id LIMIT 0 , 30
didn't work.
You can use the below query:
SELECT T1.id, T1.name, T2.name as parentname
FROM TABLE1 T1
INNER JOIN TABLE1 T2 ON T1.id = T2.parent_id
WHERE T2.ID = 5
SQL FIDDLE
This work's if you have only 1 parent at a time (no recursion):
SELECT a.name name, b.name parent_name
FROM tablexyz a,tablexyz b where
a.id=5 AND a.parent_id=b.id;
This worked fine for me. Please check it out.
select a.id,a.name,b.name as parent from cats a,cats b where b.id=a.parent_id;
You can add any other conditions too. (make sure to use the correct table identifier; a or b)
Related
I just need to show the values that don't use the specifically ID.
I have two table
table 1
id_xx
1
2
3
4
5
table 2
id | id_xx
3 | 3
4 | 3
4 | 1
I need this results for example. I say which results from ID i need
i need this result where id=3
id_xx
1
2
4
5
or where id=4
id_xx
2
4
5
or where id=1
1
2
3
4
5
You can LEFT JOIN table1 with table2 and apply the filter in the ON clause of the JOIN, and then filter on unmatched records:
SELECT t1.id_xx
FROM table1 t1
LEFT JOIN table2 t2 ON t2.id_xx = t1.id_xx AND t2.id = ?
WHERE t2.id IS NULL
You can replace the question mark with the id that you need to check.
Demo on DB Fiddle:
Given t2.id = 3:
| id_xx |
| ----- |
| 1 |
| 2 |
| 4 |
| 5 |
Given t2.id = 4:
| id_xx |
| ----- |
| 2 |
| 4 |
| 5 |
Another approach is using a Correlated Subquery with NOT EXISTS():
SELECT t1.id_xx
FROM table1 AS t1
WHERE NOT EXISTS (SELECT 1
FROM table2 AS t2
WHERE t2.id = ? -- your input id here
AND t2.id_xx = t1.id_xx)
If you have large table(s), and are worried about performance of these queries, then you may define the following index:
For the correlated subquery, define composite index (id, id_xx) on table2.
ALTER TABLE table2 ADD INDEX(id, id_xx);
Assuming that id_xx is already a Primary Key in the table1. So, you don't need to define any index there. If not, then you can define an index on it.
I have a MySQL DB and in it there's a table with activity logs of employees.
+-------------------------------------------------+
| log_id | employee_id | date_time | action_type |
+-------------------------------------------------+
| 1 | 1 | 2015/02/03 | action1 |
| 2 | 2 | 2015/02/01 | action1 |
| 3 | 2 | 2017/01/02 | action2 |
| 4 | 3 | 2016/02/12 | action1 |
| 5 | 1 | 2016/10/12 | action2 |
+-------------------------------------------------+
And I would need 2 queries. First, to get for every employee his last action. So from this example table I would need to get row 3,4 and 5 with all columns. And second, get the latest action only for specified employee.
Any ideas how to achieve this? I'm using Spring Data JPA, but raw SQL Query would be also great.
Thank you in advance.
Ready for a fred ed...
SELECT x.*
FROM my_table x
JOIN
( SELECT employee_id
, MAX(date_time) date_time
FROM my_table
GROUP
BY employee_id
) y
ON y.employee_id = x.employee_id
AND y.date_time = x.date_time;
For your first query. Simply
SELECT t1.*
FROM tableName t1
WHERE t1.log_id = (SELECT MAX(t2.log_id)
FROM tableName t2
WHERE t2.employee_id = t1.employee_id)
For the second one
SELECT t1.*
FROM tableName t1
WHERE t1.employee_id=X and t1.log_id = (SELECT MAX(t2.log_id)
FROM tableName t2
WHERE t2.employee_id = t1.employee_id);
You can get the expected output by doing a self join
select a.*
from demo a
left join demo b on a.employee_id = b.employee_id
and a.date_time < b.date_time
where b.employee_id is null
Note it may return multiple rows for single employee if there are rows with same date_time you might need a CASE statement and another attribute to decide which row should be picked to handle this kind of situation
Demo
i have table like this:
table1:
id | item_name | entered_by | modify_by
1 | banana | 2 | 1
2 | apple | 4 | 3
3 | orance | 1 | 1
4 | pineapple | 5 | 3
5 | grape | 6 | 1
table2:
id | username
1 | admin
2 | jack
3 | danny
4 | dummy
5 | john
6 | peter
the query is work fine to select if the entered_by or modify_by do have value:
SELECT t1.id, t1.item_name,
t2enteredBy.username enteredBy,
t2modifyBy.username modifyBy
FROM table1 t1
JOIN table2 t2enteredBy ON t1.entered_by = t2enteredBy.id
JOIN table2 t2modifyBy ON t1.modify_by = t2modifyBy.id
problem: if one of the modifiy_by or entered_by field have null value, the row is now showing out, i need it to show it out as '-' if it has null value rather than hide the row completely.
SQLFIDDLE HERE
Try this out:
SELECT t1.id, t1.item_name,
COALESCE(t2enteredBy.username, '-') enteredBy,
COALESCE(t2modifyBy.username, '-') modifyBy
FROM table1 t1
LEFT JOIN table2 t2enteredBy ON t1.entered_by = t2enteredBy.id
LEFT JOIN table2 t2modifyBy ON t1.modify_by = t2modifyBy.id
Fiddle here.
You need a left join to return those rows with null values. Then the coalesce will make sure that they are replaced by the given string if they are null.
Try this - use LEFT JOIN instead of JOIN
SELECT t1.id, t1.item_name,ifnull(t2enteredBy.username,'-') enteredBy,
ifnull(t2modifyBy.username,'-') modifyBy
FROM table1 t1
LEFT JOIN table2 t2enteredBy ON t1.entered_by = t2enteredBy.id
LEFT JOIN table2 t2modifyBy ON t1.modify_by = t2modifyBy.id
SQL Fiddle Here
Database: mysql > ver 5.0
table 1: type_id (int), type
table 2: name_id, name, is_same_as = table2.name_id or NULL
table 3: id, table2.name_id, table1.type_id, value (float)
I want to sum values, and count values in table 3 where table2.name_id are same and also include the values of id where is_same_is=name_id. I want to select all data in table3 for all values in table2.
Apologize if my question is not very clear, and if it has already been answered but I am unable to find a relevant answer. Or dont exactly know what to look for.
[data]. table1
id | type
=========
1 | test1
2 | test2
[data].table2
name_id | name | is_same_as
==============================
1 | tb_1 | NULL
2 | tb_2 | 1
3 | tb_3 | NULL
4 | tb_4 | 1
[data].table3
id | name_id | type_id | value
======================================
1 | 1 | 1 | 1.5
2 | 2 | 1 | 0.5
3 | 2 | 2 | 1.0
output:
name_id| type_id|SUM(value)
=======================================================
1 | 1 |2.0 < because in table2, is_same_as = 1
2 | 2 |1.0
I think the following does what you want:
select coalesce(t2.is_same_as, t2.name_id) as name_id, t3.type_id, sum(value)
from table_3 t3 join
table_2 t2
on t3.name_id = t2.name_id
group by coalesce(t2.is_same_as, t2.name_id), t3.type_id
order by 1, 2
It joins the table on name_id. However, it then uses the is_same_as column, if present, or the name_id if not, for summarizing the data.
This might be what you are looking for: (I haven't tested it in MySQL, so there may be a typo)
with combined_names_tab (name_id, name_id_ref) as
(
select name_id, name_id from table2
union select t2a.name_id, t2b.name_id
from table2 t2a
join table2 t2b
on (t2a.name_id = t2b.is_same_as)
)
select cnt.name_id, t3.type_id, sum(t3.value) sum_val
from combined_names_tab cnt
join table3 t3
on ( cnt.name_id_ref = t3.name_id )
group by cnt.name_id, t3.type_id
having sum(t3.value) / count(t3.value) >= 3
Here's what the query does:
First, it creates 'combined_names_tab' which is a join of all the table2 rows that you want to GROUP BY using the "is_same_as" column to make that determination. I make sure to include the "parent" row by doing a UNION.
Second, once you have those rows above, it's a simply join to table3 with a GROUP BY and a SUM.
Note: table1 was unnecessary (I believe).
Let me know if this works!
john...
I have a table of preferences, called "txp_prefs". I would like to return multiple preferences into a single row; the reason I prefer this to a simple concatenation is that I'm using a plugin in textpattern which can process the single row.
Here is the testing data I have:
------------------------------------------------
|Id | event | name |value |
------------------------------------------------
| 1 | season | season_start | 12/10/2011 |
-----------------------------------------------
| 2 | season | season_end | 29/10/2011 |
------------------------------------------------
| 3 | season | season_countdown | 7 |
------------------------------------------------
| 4 | another | test1 | result1 |
------------------------------------------------
| 3 | | test2 | result2 |
------------------------------------------------
The final result I would like to get is:
----------------------------------------------------------
|event | season_start | season_end | season_countdown |
----------------------------------------------------------
|season | 12/10/2011 | 29/10/2011 | 7 |
----------------------------------------------------------
I can (obviously) create the separate queries to get each result independently; for example
SELECT t1.event, t1.val AS season_start FROM txp_prefs t1 WHERE t1.event="season" AND t1.name="season_start" (to get the season_start)
SELECT t2.event, t2.val AS season_end FROM txp_prefs t2 WHERE t2.event="season" AND t2.name="season_end" (to get the season_end)
But I get errors when I try to join the two together, eg like this:
SELECT t1.event, t1.val AS season_start FROM txp_prefs t1 WHERE t1.event="season" AND t1.name="season_start"
LEFT JOIN
(SELECT t2.event, t2.val AS season_end FROM txp_prefs t2 WHERE t2.event="season" AND t2.name="season_end") t3
ON t1.event=t3.event
The error messages says it is something to do with the join (which I guessed anyway - the two individual queries work.
Any ideas? I have recently figured through joining different tables together, so I assume it is possible to join a table to itself.
Based on the structure given you can use
SELECT
MAX(CASE WHEN name = 'season_start' THEN value END) AS season_start,
MAX(CASE WHEN name = 'season_end' THEN value END) AS season_end,
MAX(CASE WHEN name = 'season_countdown' THEN value END) AS season_countdown
FROM txp_prefs
WHERE event='season'
You can do this by pivoiting. Asper my past project I demostrate you in following query hope will be useful to you.
My table transaction is having following fields
NAME VARCHAR2(10)
branch_code NUMBER(4)
Ruppes NUMBER(4)
SQL> select * from transaction;
NAME branch_code Ruppes
---------- ---------- ----------
Hemang 2602 1000
Hemang 2603 2000
Hemang 2400 3000
Yash 2602 1500
Yash 2603 1200
Yash 2400 1340
Krupesh 2602 1250
Krupesh 2603 2323
Krupesh 2400 8700
9 rows selected.
Now pivoting.
SQL> select branch_code,
2 max( decode( name, 'Hemang', Ruppes, null ) ) "Hemang",
3 max( decode( name, 'Yash', Ruppes, null ) ) "Yash",
4 max( decode( name, 'Krupesh', Ruppes, null ) ) "Krupesh"
5 from
6 (
7 select name, branch_code, Ruppes
8 from transaction
9 )
10 group by branch_code ;
branch_code Hemang Yash Krupesh
---------- ---------- ---------- ----------
2602 1000 1500 1250
2603 2000 1200 2323
2400 3000 1340 8700
select you are looking for is:
SELECT distinct
t0.event,
t1.val AS season_start ,
t2.val as seasson_end,
t3.val as season_countdown
FROM
txp_prefs t0
left outer join
txp_prefs t1
on ( t1.event=t0.event AND t1.name="season_start" )
left outer join
txp_prefs t2
on ( t2.event=t0.event AND t2.name="season_end" )
left outer join
txp_prefs t3
on ( t3.event=t0.event AND t3.name="season_countdown" )
WHERE
t0.event="season"
(the standard way to get only one row is 'distintc' reserved word. Another solution is append 'LIMIT 1' to query, but this is MySQL dependant)
are you sure that your database is right normalized?
see you.