Sometimes requirement arises to display a field value as column name in output and adjacent values in the same row below it as its values.
Suppose I have a table “students” with marks of each student in different subjects. Each student may not appear in every subject:
students
We want Read more…
Create and Download CSV of table Records using OUTFILE Sql command and PHP
1. Create temporary CSV file using OUTFILE SQL command: OUTFILE command is used to write your sql command output to the specified location. You can write the output to some files using OUTFILE when required Read more…
SQL Report in ‘Configurable Reports’ plugin provides us an easy UI to write SQL Query and draw results immediately without involving any code complications.
Suppose I want to generate my custom grades report based on some specific activities from course – Let’s say these are PreTest 1, Pretest 2 and Read more…
‘Like’ operator of SQL can be used in the following ways in Moodle:
Using expression $DB->sql_like:
$grade_item_test = $DB->get_records_sql ( ‘SELECT * FROM {grade_items} WHERE
‘.$DB->sql_like(‘idnumber’, ‘:idnum’).’ AND courseid=:cid order by itemmodule’,
array (‘idnum’=>’test’,’cid’=> $courseid) );
Using like operator:
$grade_item_test = $DB-> Read more…
JSONB (JSON Blob) datatype in Postgres is used to save JSON data. We can search on JSONB type of column after creating an index on it.
For example:
Usage in PostgreSQL:
1. Create table and index
CREATE TABLE tests
(
id integer NOT NULL,
email citext NOT NULL,
address jsonb NOT Read more…
MySQL access Denied for user while Username and password is correct.
I got this error when I named one of my table columns as “order” which is also a mysql keyword. When tried to rename it, I got the following error on execution.
ERROR 1045 (28000): Access denied Read more…
Purpose is to automate most of recurring processes like creating user, installing application (apache, apache-tomcat, mysql-server …etc), and modifying security file to hardening Linux machines in AWS environment.
1. Click AWS OpsWorks option from AWS console panel:
2. Now click on Add Stack to create a new Stack Read more…
AWS WAF web application firewall service is built to protect cloud apps from web attacks like DDoS attacks, SQL injections, Cross site scripting.
Below are the steps involved in configure AWS WAF security:
Step.1 Open CloudFormation and click on create new Stack.
Step.2 Select the option (Specify an Read more…
First method:
1. Click on the database (from list of databases on the phpMyAdmin home screen) in which you want to rename table name.
2. You will see a list of tables on click of the database.
3. Select the table and there is a dropdown below the tables with Read more…
PDO stands for PHP Data Objects. PDO is a consistent way to access databases.
Today, mostly websites or desktop based applications store their data in databases. Therefore, PHP has also provided the way to connect with databases.
PHP supports following ways to connect to the database:
1. Mysql Read more…
Problem: In our application, we have created the session token to provide secure access. We were using current system time stamp in our token as one of the key component. But after upgrading MySQL 5.5 to MySQL 5.7, we were getting random results. Most of the Read more…
In Postgresql we can save the default timestamp with now() method:
CREATE TABLE test
(
id serial NOT NULL,
name character varying(255),
last_modified_time timestamp without time zone DEFAULT now()
)
This will save the date timestamp in this format:
If we want to use the last_modified_time in code we usually convert Read more…
How to enable or disable autocommit of changes in MySQL using MySQL workbench?
Go to Edit->Preferences->SQL Editor->SQL Execution and check your current settings:
Also commit/rollback can be done with the buttons on SQL tab Read more…
AWS: Upgrading MySQL version
Below are few step to upgrade Mysql version very easily on AWS-RDS:
1. Log on to AWS console.
2. Open AWS RDS from Database section:
3. Click on Instances:
4. Select the Database Instance which you want to upgrade:
5. Right Click on Read more…
While working on two servers, we can take the backup of database on one server using mysqldump command in php.
Example :
exec(‘mysqldump –host ‘.$dbhost.’ –user ‘.$dbuser.’ –password=’.$dbpass.” “. $dbname.’ > ‘.$dbname.’.sql’);
After creating dump of database, user can move the dump database file from one server to another Read more…
Scaffolding in CakePHP
Application scaffolding in CakePHP is a technique that allows the developer to define and create a basic application that can create, retrieve, update and delete objects. Basically CRUD (create, Read, Update, Delete) data operations are common in most of the applications.
Scaffolding basically provides temporary structure or Read more…
You can create a dblink to a remote database in postgresql and query both local and remote together. Steps and an example below:
1. Enable dblink in postgresql
CREATE EXTENSION dblink;
2. Create connection with database server
SELECT dblink_connect(‘dbname=abc port=1234 host=abc user=abc password=abc’);
1. Always define hashCode() and equals() methods in your Persistent classes.
2. Persistent class method’s equals() and hashCode() must access its fields through getter methods. It is a good practice to use accessor methods instead of direct instance variable access.
3. Always Implement Serialization with your entity classes. It Read more…
In Amazon Linux, it is not yet packaged with php5.6. When we install PHP by a standrad command:
$yum install php*
1. It will install PHP version 5.3
Below are the steps to update PHP version from 5.3 to 5.6 in Amazon Linux:
Remove Read more…
In the program of uploading files to a server location, instead of using absolute location for saving file to that path, relative path needs to be used. Program was working correctly for absolute path.
In the maven project with the following directory structure , I created a resources folder in the Read more…
