Questions tagged [mysql]
MySQL is a free, open-source Relational Database Management System (RDBMS) that uses Structured Query Language (SQL). DO NOT USE this tag for other DBs such as SQL Server, SQLite etc. Those are different DBs that all use their own dialects of SQL to manage the data. Always specify the exact version of the server in the question. Note that configuration/setup-related questions are off-topic on stackoverflow.
mysql
45,930
questions
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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'];
...
2723
votes
14
answers
260k
views
Why shouldn't I use mysql_* functions in PHP?
What are the technical reasons for why one shouldn't use mysql_* functions? (e.g. mysql_query(), mysql_connect() or mysql_real_escape_string())?
Why should I use something else even if they work on ...
- 174k
1358
votes
13
answers
212k
views
UTF-8 all the way through
I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.
Where ...
- 22.4k
794
votes
13
answers
320k
views
When to use single quotes, double quotes, and backticks in MySQL
I am trying to learn the best way to write queries. I also understand the importance of being consistent. Until now, I have randomly used single quotes, double quotes, and backticks without any real ...
- 27.5k
788
votes
4
answers
315k
views
SQL injection that gets around mysql_real_escape_string()
Is there an SQL injection possibility even when using mysql_real_escape_string() function?
Consider this sample situation. SQL is constructed in PHP like this:
$login = mysql_real_escape_string(...
- 82.8k
1664
votes
27
answers
2.1m
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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 ...
- 30k
47
votes
1
answer
232k
views
Syntax error due to using a reserved word as a table or column name in MySQL
I'm trying to execute a simple MySQL query as below:
INSERT INTO user_details (username, location, key)
VALUES ('Tim', 'Florida', 42)
But I'm getting the following error:
ERROR 1064 (42000): You ...
388
votes
10
answers
484k
views
How can I return pivot table output in MySQL?
If I have a MySQL table looking something like this:
company_name
action
pagecount
Company A
PRINT
3
Company A
PRINT
2
Company A
PRINT
3
Company B
EMAIL
Company B
PRINT
2
Company B
PRINT
2
...
- 5,073
114
votes
5
answers
111k
views
Trouble with UTF-8 characters; what I see is not what I stored
I tried to use UTF-8 and ran into trouble.
I have tried so many things; here are the results I have gotten:
???? instead of Asian characters. Even for European text, I got Se?or for Señor.
Strange ...
- 140k
1336
votes
34
answers
1.2m
views
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 ...
- 27.3k
372
votes
14
answers
791k
views
Connect Java to a MySQL database
How do you connect to a MySQL database in Java?
When I try, I get
java.sql.SQLException: No suitable driver found for jdbc:mysql://database/table
at java.sql.DriverManager.getConnection(...
- 9,338
1005
votes
31
answers
777k
views
mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource
I am trying to select data from a MySQL table, but I get one of the following error messages:
mysql_fetch_array() expects parameter 1 to be resource, boolean given
This is my code:
$username = $...
- 25k
83
votes
5
answers
458k
views
How to include a PHP variable inside a MySQL statement
I'm trying to insert values in the contents table. It works fine if I do not have a PHP variable inside VALUES. When I put the variable $type inside VALUES then this doesn't work. What am I doing ...
- 10.2k
450
votes
17
answers
459k
views
How to create a MySQL hierarchical recursive query?
I have a MySQL table which is as follows:
id
name
parent_id
19
category1
0
20
category2
19
21
category3
20
22
category4
21
...
...
...
Now, I want to have a single MySQL query to which I simply ...
- 4,745
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votes
2
answers
2.2m
views
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?
- 33.5k