[MySql] How to add/delete a column from commandline

Following command is used to delete a column from a table:

ALTER TABLE <table_name> DROP COLUMN <column_name>;

Following command is used to add a column in table:

ALTER TABLE <table_name> ADD <column_name> <datatype> ;

[MySql] How to export MySql database schema using command line

Following command dumps MySql database's schema into a file:

mysqldump -u<username>i -p<password> -h<host> --databases <database1> --no-data > dump.sql

Above command exports single or multiple databases into dump.sql. This only exports database schema without any table contents.


This exported schema can be restored using following command:


mysql -u<username>i -p<password> -h<host> <database_name> < dump.sql

Uploading files to Remote Server

There are different ways we can upload files to remote servers. Few command line tools are listed here"
1- Securely Copy files (scp):
scp -v -r -o IdentityFile=<cert.pem> <source folder> <user>@<remoteserverip>:/home/<user>/<destination folder>

Note: If a certificate is needed, then IdentityFile=<cert.pem> should be used.

2- rSync: 
rsync -vcrz --delete-after <source folder> <user>@<remoteserverip>:/home/<user>/<destination folder>

jQuery Chaining Interview question

Which one of the following will break the chain and Why?
A-

$(…)
.html('Breaks chain')
.addClass('chainbreaker')

B-

$(…)
.html()
.addClass('chainbreaker')

Solution:
In A, .html('Breaks chain') behaves like a setter and returns object, on which .addClass(…) adds the given class. But in B, .html() behaves like a getter and returns a string, on which .addClass(…) methods fails to perform and gives runtime error.