This Is Your Brain On Informatics: MariaDB

mysql -u [username] -p

The above command will give access to the MariaDB for a username that has previously been created. The next line will prompt for a password.

SQL

The language of Maria DB.

Common Commands in SQL
Boolean Operators
AND
OR
NOT
Command*	Syntax	Description
`table`		Syntax for indicating a table
AS var		Sets an output to a variable
AUTO_INCREMENT		Automatically adds +1 to an entry for a column for each successive entry
AVG()		Gives an average of the values in the indicated column
BIGINT		64-bit integer
CHAR		Assigns a character variable (allows ONLY 1 character)
CREATE TABLE `table`	Creates a table of the given name with the properly input variable (see below)
CREATE TEMPORARY TABLE `[table]`		Creates a temporary table of the given name
DATE		Assigns a date variable of the form 00-00-0000
FROM		Denotes which table SELECT pulls the columns from (e.g. SELECT [col1],[col2] FROM `table`
INSERT	INSERT INTO table_name VALUES (value1,value2,value3,...); INSERT INTO table_name (column1,column2,column3,...) VALUES (value1,value2,value3,...); -- specifies the columns the values go into	Used with INTO to insert new data entries into the specified columns
INT		32-bit integer
INTO	SELECT * or column_name(s) INTO newtable [IN externaldb] FROM table1;	Used with SELECT command to copy column_names from table1 into newtable
LIMIT #		Limits to the top # number of entries (not necessarily by rank)
MAX()		Gives the maximum of the values in the indicated column
MIN()		Gives the minimum of the values in the indicated column
PRIMARY KEY		Indicates which variable will differentiate each data entry
SELECT		Selects columns from a database for analysis
UNSIGNED		only allows positive integers or float values, always assigned after BIGINT or INT value
UPDATE	UPDATE table_name SET column1=value1,column2=value2,... WHERE some_column=some_value;	Changes column1 to value1 based on the WHERE statement (use something unique to update only one row)
USE database		Selects database for manipulation and analysis
VARCHAR(#)		Assigns a character array variable of length #
WHERE		Limits the available values SELECT can pull from each column based on a logical statement (e.g. WHERE col1 < 10)

*Commands are capitalized by convention.

In-Class Example of Manually Creating a Table

This data table was uploaded as a TSV (tab separated values) file.

LOAD DATA INFILE '[data table pathname]' INTO TABLE `test` FIELDS TERMINATED BY '\t' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY '\r\n' IGNORE 1 LINE

Answer to In-Class Question

Q: Find the maximums in column 2 of quintiles based on column 1

The following will create a temporary table that will order [var1], hold [var2] and also create a column with a counter variable named "id".

A: CREATE TEMPORARY TABLE `rank` (id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY) SELECT [var1],[var2] FROM `test` WHERE [var3] = "string" AND [var1] <10000000 ORDER BY [var1];

Then the use of the next command will need to be repeated for each quintile to find the maximum for each one.

A: SELECT MAX([var2]) FROM `rank` WHERE id BETWEEN [calculated lower bound of quintile] AND [calculated upper bound of quintile];