This Is Your Brain On Informatics: MariaDB
MariaDB is an opensource project that is an offshoot of MySQL because the developers felt that Oracle was doing a poor job managing MySQL (actually, the developers came from Oracle). Because MariaDB was built to be a better managed version of MySQL, many of the resources on the internet for MySQL will be applicable for MariaDB. Below are several topics on MariaDB to make it operate in the context of an NGINX server.
Contents
MariaDB SQL Commands
The language of Maria DB.
| Common Commands in SQL | ||
|---|---|---|
| Boolean Operators | ||
| AND | ||
| OR | ||
| NOT | ||
| Command* | Syntax | Description |
| mysql | mysql -u username -p | Command line command where username should be replaced by the user's account name |
| `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.
MariaDB Examples
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];
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