All Questions
134,393
questions
2773votes
28answers
2.0mviews
How can I prevent SQL injection in PHP?
If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example:
$unsafe_variable = $_POST['user_input'];
...
2486votes
54answers
4.3mviews
How do I import an SQL file using the command line in MySQL?
I have a .sql file with an export from phpMyAdmin. I want to import it into a different server using the command line.
I have a Windows Server 2008 R2 installation. I placed the .sql file on the C ...
- 36k
2010votes
3answers
1.9mviews
What's the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN? [duplicate]
What's the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN
in MySQL?
- 30.7k
1501votes
27answers
1.7mviews
SQL select only rows with max value on a column [duplicate]
I have this table for documents (simplified version here):
id
rev
content
1
1
...
2
1
...
1
2
...
1
3
...
How do I select one row per id and only the greatest rev?
With the above data, the ...
- 27.6k
1476votes
24answers
1.5mviews
How to reset AUTO_INCREMENT in MySQL
How can I reset the AUTO_INCREMENT of a field?
I want it to start counting from 1 again.
- 18.3k
1393votes
15answers
796kviews
Can I concatenate multiple MySQL rows into one field?
Using MySQL, I can do something like:
SELECT hobbies FROM peoples_hobbies WHERE person_id = 5;
My Output:
shopping
fishing
coding
but instead I just want 1 row, 1 col:
Expected Output:
shopping, ...
- 30.4k
1201votes
32answers
910kviews
Retrieving the last record in each group - MySQL
There is a table messages that contains data as shown below:
Id Name Other_Columns
-------------------------
1 A A_data_1
2 A A_data_2
3 A A_data_3
4 B ...
- 25.7k
1051votes
12answers
664kviews
INNER JOIN ON vs WHERE clause
For simplicity, assume all relevant fields are NOT NULL.
You can do:
SELECT
table1.this, table2.that, table2.somethingelse
FROM
table1, table2
WHERE
table1.foreignkey = table2.primarykey
...
- 15.2k
1045votes
11answers
1.1mviews
Insert into a MySQL table or update if exists
I want to add a row to a database table, but if a row exists with the same unique key I want to update the row.
For example:
INSERT INTO table_name (ID, NAME, AGE) VALUES(1, "A", 19);
Let’s ...
- 13.2k
998votes
20answers
535kviews
Join vs. sub-query
I am an old-school MySQL user and have always preferred JOIN over sub-query. But nowadays everyone uses sub-query, and I hate it; I don't know why.
I lack the theoretical knowledge to judge for ...
- 154k
995votes
11answers
958kviews
How can I do 'insert if not exists' in MySQL?
I started by googling and found the article How to write INSERT if NOT EXISTS queries in standard SQL which talks about mutex tables.
I have a table with ~14 million records. If I want to add more ...
- 30.2k
866votes
21answers
1.8mviews
How can I SELECT rows with MAX(Column value), PARTITION by another column in MYSQL?
My table is:
id
home
datetime
player
resource
1
10
04/03/2009
john
399
2
11
04/03/2009
juliet
244
5
12
04/03/2009
borat
555
3
10
03/03/2009
john
300
4
11
03/03/2009
juliet
200
6
12
03/03/2009
...
- 9,323
785votes
15answers
905kviews
How can I do a FULL OUTER JOIN in MySQL?
I want to do a full outer join in MySQL. Is this possible? Is a full outer join supported by MySQL?
- 19.4k
751votes
10answers
756kviews
How can I temporarily disable a foreign key constraint in MySQL?
Is it possible to temporarily disable constraints in MySQL?
I have two Django models, each with a foreign key to the other one. Deleting instances of a model returns an error because of the foreign ...
- 34.8k
746votes
15answers
770kviews
MySQL Query GROUP BY day / month / year
Is it possible to make a simple query to count how many records I have in a determined period of time like a year, month, or day, having a TIMESTAMP field, like:
SELECT COUNT(id)
FROM stats
WHERE ...
