1
vote
1answer
40 views

optimize the query with big and low cardinality

I have big enough dataset and few joins to get them all with help next query: SELECT DISTINCT c.c_id FROM c_active z1 INNER JOIN cs c ON (z1.cv_id=c.cv_id) INNER JOIN indi i ON (c.m_id=i.m_id) INNER ...
3
votes
2answers
90 views

SQL Question: Selecting different language versions based on availability

I have the following situation: I have a table that contains entries with language versions (German and English) as part of the key (the other part being a "name" field). However, not always both ...
0
votes
0answers
40 views

Tips for improving my particular batch processing

I'm working with mail data from the USPS, which contains 10 related tables to make up a single mailing, as well as a single table containing all of the scans that each mail piece may receive. Once per ...
0
votes
1answer
85 views

MySQL 5.6.14 will not use proper key/index in query

OS: ubuntu 12.04 amd64 DB: MySQL 5.6.14-community amd64 I cannot figure out why this query is using the wrong index and doing a full table scan on the ar_batch (ab) table. Perhaps someone can see ...
0
votes
0answers
71 views

unexpected null returned from calculated columns

I'm working on a program that will calculate journey times based on bluetooth MAC addresses and i'm trying to nail down the mySQL commands I need before I get cracking on the software part of it. i ...
2
votes
2answers
196 views

Changing ORDER BY direction causes performance issue

I use MySQL 5.6, and I have two tables each with 16M rows: CREATE TABLE IF NOT EXISTS `newsstudios` ( `id` int(11) NOT NULL AUTO_INCREMENT, `title` varchar(255) COLLATE utf8_unicode_ci NOT NULL, ...