The SELECT statement is used to specify which columns of a database table should be included in the result.
Limiting the number of rows returned from a table is a useful trick for speeding query time. To limit the number of rows, you can use the LIMIT command.
To rename a column or a table when returning results, you can use the AS command to set an alias for your outputs.
Datasets often contain duplicate rows or values in a column. Combining SELECT with DISTINCT drops duplicates.
COUNT() returns the number of rows in the table or group.
MIN() returns the minimum value in a numeric column.
MAX() returns the maximum value in a numeric column.
SUM() returns the total of numeric values.
AVERAGE calculates the arithmetic mean of a column.
The WHERE clause filters rows that match a certain condition.
HAVING clause is similar to the WHERE clause, but it can only be used with aggregate functions while WHERE can’t.
AND operator is used when filtering rows that match more than one condition.
OR is another conditional operator that allows you to subset rows if any of the conditions separated by OR are true.
BETWEEN allows you to subset rows within a certain range, which makes WHERE clauses simpler and easier to read.
The IN operator is a shorthand for multiple OR statements.
The LIKE operator lets you search for patterns in a text column using special strings called wildcards.
GROUP BY lets you group rows based on column values.
ORDER BY lets you order rows based on a column value. You can order by ascending (default) or descending order by adding the ASC or DESC.
UPDATE is used to change the values of individual cells in an existing table. It is used with the SET keyword.
You can use the ALTER TABLE statement to modify the properties of the table and its columns (not actual cell values).
CREATE TABLE creates a new table in a database.
INSERT INTO statement can be used to add new rows to a table.
The INNER JOIN command selects rows that have matching values in both tables.
A LEFT JOIN keeps all of the original records in the left table and returns missing values for any columns from the right table where the joining field did not find a match.
A RIGHT JOIN keeps all of the original records in the right table and returns missing values for any columns from the left table where the joining field did not find a match.