Tagged Questions
0
votes
0answers
42 views
one vs two column index difference when doing JOIN query?
Let`s suppose that alfa,beta and gamma contains milions of rows so we need to create indexes obviously to get optimal performace for this query :
SELECT * FROM alfa
JOIN beta on beta.id = ...
1
vote
0answers
29 views
parenthetic grouping of join clauses
What is the difference between these joins?
a left join b left join c
(a left join b) left join c
a left join (b left join c)
Does the grouping only affect the order of the joins? Will the query ...
0
votes
1answer
149 views
Group By on column from joined table
its about the following query.
EXPLAIN SELECT phrase, infinitiv
FROM `dict_verbs_all` `t`
INNER JOIN `dict_verbs_all_language` `verbsGerman_c`
ON (`t`.`id`=`verbsGerman_c`.`verb_id`)
INNER JOIN ...
3
votes
1answer
1k views
how to fetch different data on compare rows of two tables
I have two tables in my database, one is user_app table in which user info are stored, table are as:
+--------------+--------------+------+-----+-------------------+-----------------------------+
| ...
2
votes
1answer
131 views
MySQL: Very slow query, not using index, no joins involved
I am running what I think is a very simple query:
SELECT SQL_NO_CACHE m.mbr_nbr
FROM tran.member m
WHERE m.cardnbr = 000099999930
The table member is a poorly written one, with 133 columns and ...
1
vote
2answers
589 views
Improving performance of nasty nested-view joins
I have a moderate-sized database spread out over a few tables, the rough architecture is:
Input Data (Data ID, Session ID and a few fields of statistical importance)
Input File (Data ID and a blob)
...
3
votes
2answers
573 views
Index on primary key not used in simple join
I have the following table and index definitions:
CREATE TABLE munkalap (
munkalap_id serial PRIMARY KEY,
...
);
CREATE TABLE munkalap_lepes (
munkalap_lepes_id serial PRIMARY KEY,
...
