Category Archives: Tech

How to Optimize your WiFi Signal and Speed Up your Web Surfing

Are you suffering from frequent connection drops or slower download speed?
Are you located in a relatively densely populated area?

If your are surfing the web in a densely populated area, it is likely that multiple WiFi networks are within range. If you experience frequent connection drops or slower speed, it is most likely due to multiple network signals competing for the same channel.

Here is a simple 2 step solution for that.
 
Continue reading “How to Optimize your WiFi Signal and Speed Up your Web Surfing” »

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How to I install python 2.7.5 on Ubuntu – 4 Simple Steps

1. Install dependencies
sudo apt-get install build-essential checkinstall
sudo apt-get install libreadline-gplv2-dev libncursesw5-dev libssl-dev libsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev
2. Download python
cd ~/Downloads/
wget http://python.org/ftp/python/2.7.5/Python-2.7.5.tgz
3. Extract download
tar -xvf Python-2.7.5.tgz

Continue reading “How to I install python 2.7.5 on Ubuntu – 4 Simple Steps” »

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JSON validator

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SQL (Structured Query Language) Cheat Sheet

Operators

=
Equal

 

<>
Not equal

 

>
Greater than

 

<
Less than.

 

>=
Greater than or equal.

 

<=
Less than or equal.

 

BETWEEN
Between an inclusive range.

 

IN
Search for exact value in a list.

 

LIKE
Search for a pattern.

 

%
Wildcard/s in a pattern.

 

AND
Used between arguments in WHERE statement.

 

OR
Used between arguments in WHERE statement

 

ASC
Alphabetical and numerical order – default for ORDER BY statement

 

DESC
Reverse alphabetical and numerical order

 

Data Types

integer(size)
Integers only. Maximum number of digits specified in parenthesis.

 

int(size)
Integers only. Maximum number of digits specified in parenthesis.

 

smallint(size)
Integers only. Maximum number of digits specified in parenthesis.

 

tinyint(size)
Integers only. Maximum number of digits specified in parenthesis.

 

decimal(size,d)
Hold numbers with fractions. Maximum number of digits specified in “size”. Maximum number of digits to the right of the decimal is specified in “d”.

 

numeric(size,d)
Hold numbers with fractions. Maximum number of digits specified in “size”. Maximum number of digits to the right of the decimal is specified in “d”.

 

char(size)
Holds a fixed length string (can contain letters, numbers, and special characters). The fixed size is specified in parenthesis.

 

varchar(size)
Holds a variable length string (can contain letters, numbers, and special characters). The maximum size is specified in parenthesis.

 

date(yyyymmdd)
Holds a date

 

Functions

SUM(column)
Return the total sum of columns’ values

 

AVG(column)
Return the average value of a column

 

COUNT(column)
Return the number of rows (excluding NULL) of a column

 

MAX(column)
Return the highest value of a column

 

MIN(column)
Return the lowest value of a column

 

Database Manipulation

Create database
CREATE DATABASE database_name

 

Delete database
DROP DATABASE database_name

 

Table Manipulation

Create table
CREATE TABLE “table_name”
(“column_1” “data_type_for_column_1”,
“column_2” “data_type_for_column_2”,
… )

 

Add column to a table
ALTER TABLE table_name
ADD column_name datatype

 

Delete column from a table
ALTER TABLE table_name
DROP column_name datatype

 

Delete table
DROP TABLE table_name

 

Index Manipulation

Create index
CREATE INDEX index_name
ON table_name (column_name_1, column_name_2, …)

 

Create a unique index
CREATE UNIQUE INDEX index_name
ON table_name (column_name_1, column_name_2, …)

 

Delete index
DROP INDEX table_name.index_name

 

Data Manipulation

Insert new rows into a table
INSERT INTO table_name VALUES (value_1, value_2,….)
or
INSERT INTO table_name (column1, column2,…)
VALUES (value_1, value_2,….)

 

Update column/s
UPDATE table_name
SET column_name_1 = new_value_1, column_name_2 = new_value_2
WHERE column_name = some_value

 

Delete row/s
DELETE FROM table_name
WHERE column_name = some_value

 

Delete the data from a table
TRUNCATE TABLE table_name

 

Select

Select all data from a table
SELECT *
FROM table_name

 

Select all data from specified columns
SELECT column_name(s)
FROM table_name

 

Select using alias
SELECT table_alias.column_name AS column_alias
FROM table_name AS table_alias

 

Select only distinct (different) data from a table.
SELECT DISTINCT column_name(s)
FROM table_name

 

Limit selection
Select data using WHERE, AND, OR
SELECT column_name(s) FROM table_name
WHERE column operator value
AND column operator value
OR column operator value

 

Select data using IN.
SELECT column_name(s) FROM table_name
WHERE column_name IN (value1, value2, …)

 

Order selection
Order results buy column value ascending or descending.
SELECT column_name(s) FROM table_name
ORDER BY column_1 DESC/ASC

 

Join selection
Select all matching rows from 2 tables.
SELECT column_1_name, column_2_name, …
FROM first_table_name
INNER JOIN second_table_name

 

Select all rows from the first table, even if there are no matches in the second table.
SELECT column_1_name, column_2_name, …
FROM first_table_name
LEFT JOIN second_table_name
ON first_table_name.key = second_table_name.foreign_key

 

Select all rows from the second table, even if there are no matches in the first table.
SELECT column_1_name, column_2_name, …
FROM first_table_name
RIGHT JOIN second_table_name
ON first_table_name.key = second_table_name.foreign_key

 

Add up selections
Select all the values from multiple SQL statements.
SQL_Statement_1
UNION ALL
SQL_Statement_2

 

Select all the different values from multiple SQL statements.
SQL_Statement_1
UNION
SQL_Statement_2 Select

 

Populate with selection
Select and insert into another table.
SELECT column_name(s)
INTO new_table_name
FROM source_table_name
WHERE …

 

Select and insert into another database.
SELECT column_name(s)
IN external_database_name
FROM source_table_name
WHERE …

 

Populate a virtual table with the result-set of a SELECT statement.
CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE …

 

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