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PHP MySQL query with error printingHow to write SQL using PHP to handle the data in MySQL database? In any database
driven script we have to update, add, modify, data in the tables. By using PHP
we can do all this using different functions available in PHP. We will start
with very basic function, which will execute any query written in sql and can be
applied to MySQL database.
SQL
Structured Query Language or popularly known as SQL is an universal language to handle
database. An introduction and different types of sql command like select,
insert, update etc you will get in the sql section of this site. There are some
advance SQL commands like left join, linking of tables etc to study. If you are
not comfortable with SQL any time you can refer the materials in sql section.
There are three steps invoved in this process.
- Connection to database
- Build the query and execute
- Display the data
First ensure that you have established your mysql connection through PHP. To
get the full details on php mysql connection you can read the article here. If you are using PDO then start with PDO connection string here.
PHP Functions & SQL
Let us start with the function required to execute one query in PHP. Once you have connection established then we can execute sql command by using PHP function mysql_query(). Here is the syntax of the function.
Let us first write the query and store in a variable. We will write a query to
create table.$query="CREATE
TABLE student ( id int(2) NOT NULL auto_increment, name varchar(50) NOT NULL
default '', class varchar(10) NOT NULL default '', mark int(3) NOT NULL default
'0', PRIMARY KEY (id) ) TYPE=MyISAM";
We have stored the sql create query in a variable $query and we will pass this as a
parameter to the function like below.
$rt=mysql_query($query);
The above command will execute the query ( stored in variable $query) and we can
check the status of the query ( successful or not ) by checking the status of
$rt. $rt will be true of the query is successfully executed or it will return
false. We will use php if command to check the status of the query.
if($rt){echo " Command is successful ";}
else
{echo "Command is not successful ";}
So from the above line we can know that the query has worked or failed. But we will
not come to know what the error is if the query has failed. To get the error
message we have to use another function mysql_error() to print the error message
returned by MySQL database after executing the query. Here it is how to print
the error message.
echo
mysql_error();
The above line will print the error returned by mysql database if the query fails to
execute. You can read more on mysql error here.
The
complete code is available below.
$query="CREATE TABLE student4 ( id int(2) NOT NULL auto_increment, name varchar(50) NOT NULL default '',
class varchar(10) NOT NULL default '', mark int(3) NOT NULL default '0', PRIMARY KEY (id) ) TYPE=MyISAM";
$rt=mysql_query($query);
echo mysql_error();
if($rt){echo " Command is successful ";}
else
{echo " Command is not successful ";}
Above this code keep the code given at mysql connection page to keep the connection open
Next step is to display the data collecting from MySQL table
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