- Data can be fetched from MySQL tables by executing SQL SELECT statement through PHP function mysqlquery. You have several options to fetch data from MySQL. The most frequently used option is to use function mysqlfetcharray. This function returns row as an associative array, a.
- In this step we get the states from our places table and insert in our first select option menu then we use onchange event which call the fetchselect; function which passes an ajax request to fetchdata.php and gets the result and insert in our second select option menu.You may also like slide in navigation menu using jQuery and CSS.
- Mysqlselectdb (string $databasename, resource $linkidentifier = NULL): bool Sets the current active database on the server that's associated with the specified link identifier. Every subsequent call to mysqlquery will be made on the active database.
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SELECT query with prepared statements You must always use prepared statements for any SQL query that would contain a PHP variable. To do so, always follow the below steps: Create a.
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Php Mysql Select From Multiple Tables
The SQL SELECT command is used to fetch data from the MySQL database. You can use this command at mysql> prompt as well as in any script like PHP.
Here is generic SQL syntax of SELECT command to fetch data from the MySQL table −
You can use one or more tables separated by comma to include various conditions using a WHERE clause, but the WHERE clause is an optional part of the SELECT command.
You can fetch one or more fields in a single SELECT command.
You can specify star (*) in place of fields. In this case, SELECT will return all the fields.
You can specify any condition using the WHERE clause.
You can specify an offset using OFFSET from where SELECT will start returning records. By default, the offset starts at zero.
You can limit the number of returns using the LIMIT attribute.
Fetching Data from a Command Prompt
Php Mysql Select From Multiple Tables
This will use SQL SELECT command to fetch data from the MySQL table tutorials_tbl.
The following example will return all the records from the tutorials_tbl table −
Fetching Data Using a PHP Script
You can use the same SQL SELECT command into a PHP function mysql_query(). This function is used to execute the SQL command and then later another PHP function mysql_fetch_array() can be used to fetch all the selected data. This function returns the row as an associative array, a numeric array, or both. This function returns FALSE if there are no more rows.
The following program is a simple example which will show how to fetch / display records from the tutorials_tbl table.
The following code block will display all the records from the tutorials_tbl table.
The content of the rows is assigned to the variable $row and the values in that row are then printed.
NOTE − Always remember to put curly brackets when you want to insert an array value directly into a string.
In the above example, the constant MYSQL_ASSOC is used as the second argument to the PHP function mysql_fetch_array(), so that it returns the row as an associative array. With an associative array you can access the field by using their name instead of using the index.
PHP provides another function called mysql_fetch_assoc(), which also returns the row as an associative array.
The following example to display all the records from the tutorial_tbl table using mysql_fetch_assoc() function.
You can also use the constant MYSQL_NUM as the second argument to the PHP function mysql_fetch_array(). This will cause the function to return an array with the numeric index.
Try out the following example to display all the records from tutorials_tbl table using the MYSQL_NUM argument.
All the above three examples will produce the same result.
It is a good practice to release cursor memory at the end of each SELECT statement. This can be done by using the PHP function mysql_free_result(). The following program is the example to show how it should be used.
Try out the following example −
While fetching data, you can write as complex a code as you like, but the procedure will remain the same as mentioned above.
Before running any query with mysqli, make sure you've got a properly configured mysqli connection variable that is required in order to run SQL queries and to inform you of the possible errors.
SELECT query with prepared statements
You must always use
prepared statements for any SQL query that would contain a PHP variable. To do so, always follow the below steps:
- Create a correct SQL SELECT statement. Test it in mysql console/phpmyadmin if needed
- Replace all variables in the query with question marks (called placeholders or parameters)
- Prepare the resulting query
- Bind all variables to the previously prepared statement
- Execute the statement
- Get the mysqli result variable from the statement.
- Fetch your data
Long story short, here is the code:
And have your SELECT query executed without a single syntax error or SQL injection.
Let's see what does every line of this code mean
Like it was said above, first we are writing an SQL query where all variables are substituted with question marks.
IMPORTANT! there should be no quotes around question marks, you are adding placeholders, not strings.
Then, the query is prepared. The idea is very smart. To avoid even a possibility of the SQL injection or a syntax error caused by the input data, the query and the data are sent to database server separately. So it goes on here: with
prepare() we are sending the query to the database server ahead. A special variable, a statement is created as a result. We would use this variable from now on.
Then variables must be bound to the statement. The call consists of two parts - the string with types and the list of variables. With mysqli, you have to designate the type for each bound variable. It is represented by a single letter in the first parameter. The number of letters should be always equal to the number of variables. The possible types are
- i for integer
- d for double (float)
- s for string
- b for blobs
A HINT: you can almost always safely use 's' for any variable.
So now you can tell that 's' means 'there would be 1 variable, of string type'.
Then the query finally gets executed. Means variables get sent to the database server and the query is actually executed.
NOTE that you don't have to check the execution result. Given you have the proper connection code mentioned above, in case of error mysqli will raise an error automatically.
Here we are calling a very smart function. By default, for some reason it's impossible to fetch a familiar array (like we did with
mysql_fetch_array()) from a mysqli statement. So this function is here to help, getting a mysqli result from a mysqli statement.
Finally, fetching a row using a familiar
Getting multiple rows into array
Generally, getting multiple rows would involve a familiar while loop:
However, in a modern web-application the database interaction is separated from the HTML output. It makes the code much cleaner and more flexible. It means that we should never print our data using a while loop but rather collect it into array and then use this array for the output.
And mysqli has a handy function that instantly returns an array from the query result:
mysqli_fetch_all(). So instead of four lines
it could be just a single line:
after which you can use the
$data for the output:
By default this function returns enumerated arrays, so to get associative arrays the
MYSQLI_ASSOC mode must be set explicitly.
SELECT query with a helper function
As you may noted, the code for a prepared statement is quite verbose. If you like to build a code like a Lego figure, with shining ranks of operators, you may keep it as is. If you, like me, hate useless repetitions and like to write concise and meaningful code, then there is a simple helper function. With it, the code will become two times shorter:
Only three lines instead of six!