Database Technologies

As discussed in previous Blogs about Hot Standby in following links: 1. Monitoring Hot Standby 2. HotStandby in PostgreSQL 9.0. I came up with the following Monitoring Script for Hot Standby. #!/bin/bash # Filename: monitor_hotstandby # Usage is $0 -m master:port -s slave:port -b "PostgreSQL Bin Directory" # Author: Vibhor Kumar # Date: Jan 4th 2011 # E-mail: vibhor.aim@gmail.com while getopts "m:s:b:" opt;do case $opt in m) h1=`echo $OPTARG|cut -d":" -f1` p1=`echo $OPTARG|cut -d":" -f2`;; s) h2=`echo $OPTARG|cut -d":" -f1` p2=`echo $OPTARG|cut -d":" -f2`;; b) PGHOME="$OPTARG" esac done PSQL=$PGHOME/psql function usage() { if [ -z $h1 ];then echo "USAGE: " echo "$0 -m master:port -s slave:port -b pg bin directory" exit 1 fi if [ -z $h2 ];then echo "USAGE: " echo "$0 -m master:port -s slave:port -b pg bin directory" exit 1 ...

This is a Question which I had seen people generally ask, when they Move their DBs to PG or PGPlus Advanced Server and Look for Workaround of Oracle Feature of Traverse of Directed Graph in PG. Oracle Provides CONNECT BY NOCYCLE for traversing a Directed Graph. As mentioned in Following link: http://www.adp-gmbh.ch/ora/sql/connect_by_nocycle.html However, CONNECT BY NOCYCLE implementation, some times miss some paths for Traversing Graph as you can see in following Example: create table directed_graph ( node_from char(1), node_to char(1) ); insert into directed_graph values ('A', 'C'); insert into directed_graph values ('A', 'B'); insert into directed_graph values ('B', 'E'); insert into directed_graph values ('C', 'H'); insert into directed_graph values ('H', 'I'); insert into directed_graph values ('I', 'D'); insert into directed_graph values ('D', 'F'); insert...

Lot of People think that COPY is only a Server Based Command. However its not completely true. User can copy the data of a table at client side using COPY Command. The Difference is only in syntax usage. User has to use backSlash before COPY Command as given below: testdb=# select * from test; id ---- 1 2 3 (3 rows) testdb=# \copy test to '/tmp/test.copy' testdb=# \q We can see output of a file at Client side as given below: cat /tmp/test.copy 1 2 3 Similarly User can also copy the data in a file to Server using \COPY as given below: \COPY test from '/tmp/test.copy' iclive1460=# \COPY test from '/tmp/test.copy' iclive1460=# select * from test; id ---- 1 2 3 1 2 3 (6 rows) Note:: One should remember while using \COPY Command, one should not terminate command with semicolon ';'

SQL Injection is method of Hacking Data inside the Database. Using SQL Injection, Hackers do multiple Attempt of SQLs to understand the Structure of tables and Try to get the hint of data inside a table. For example, if a Hacker knows that UserName and Password of a Website are stored in a database table say member, then he can write query something like given below to fetch all the data inside the function as given below: select * from tablename where 1=1; Or select * from tablename where 'x'='x'; Similarly, suppose Hacker wants to know the structure (Columns) of any table, then he can try multiple attempts of finding the column name by using the HAVING OR GROUP BY CLAUSE and can find the Columns Names Based on Error. As given below: postgres=# select * from test_sql_injection group by 1 having 1=1; ERROR: column "test_sql_injection.col" must appear in the GROUP BY clause or be used in an aggregate function LINE 1: select * from test_sql_injection gro...