An SQL join clause combines records from two or more tables or views.
2
votes
1answer
63 views
Best practice: Unions or a derived table?
I've inherited a medium-sized database with a terrible schema. The sanitized portion in question is like so:
CREATE TABLE `pending` (
...
`invoice` int(11) DEFAULT NULL,
`lid` int(11) DEFAULT ...
0
votes
1answer
58 views
Complicated join with where clause
I have four tables:
sales
sales_thumbs
sales_images
sales_sizes
sales table:
+--------------+---------------------+------+-----+---------+----------------+
| Field | Type | ...
2
votes
0answers
46 views
update statement with self join
I needed to copy information from one row of a table to another.
I noticed I could do the following:
update address
set col1 = a2.col1,
col2 = a2.col2,
.....etc
from address a1, address a2
where ...
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 ...
1
vote
0answers
58 views
How can I join one to one to (many to one) without using group_concat
I have a table structure as follows:
--
-- Table structure for table `emails`
--
CREATE TABLE IF NOT EXISTS `emails` (
`ID` int(5) NOT NULL AUTO_INCREMENT,
`email` varchar(255) COLLATE ...
1
vote
0answers
320 views
MySQL join for multiple child records in a single joined row
I have one master table (teacher) structured like
teacherId Name Class
1 Praveen 10
2 John 9
and having a child table (student) structured like
studentId ...
1
vote
0answers
133 views
Multi-Table Join to Single Destination
I am having a serious performance issue with join together four tables and placing the results (in a certain permutation) into one destination table. I am using MSSQL 2008 and good ole T-SQL.
To ...
0
votes
0answers
25 views
Missing values in INNER JOIN MS-Access?
When I run the following query in MS-Access:
SELECT a1.ConStateNumber, a2.ConStateNumber
FROM qryW2_yr_sum_slash_qryW2_q4_sum_result a1 INNER JOIN
qryW2_q3_sum a2 ON a1.ConStateNumber = ...
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 = ...
0
votes
0answers
32 views
How Can I do and INNER JOIN USING (2 columns)?
Suppose we have:
CREATE TABLE cscart_products_prices_temp LIKE cscart_products_prices;
ALTER TABLE `cscart_products_prices_temp`
DROP `percentage_discount`,
DROP `lower_limit`,
LOAD DATA LOCAL ...
0
votes
0answers
64 views
How can I get multiple rows instead of columns after self-joins?
This is my situation (the real table isn't about people but about paths):
[Table: People]
id | name | type | related_to
----------------------------
1 | | | 0
2 | Nico | Friend | ...
0
votes
0answers
111 views
Which update is faster using join or sequential?
My this question is in sequence of my previous question I asked.
I could write two solutions using Stored Procedure instead of trigger or nested-query .
Both use a helper function ...
