Commands
SQL operates through declarative statements featuring commands.
Here’s an appendix of commonly used commands.
Commands
- ALTER TABLE
- Adds, deletes, modifies or changes the data type of a column in a table.
- AS
- Renames a column or table with an alias for display, does not permanently change table/column names in the database.
- CASE
- Returns different output based on the conditions of each statement.
- CREATE INDEX
- Creates an index on existing columns in a table. Indexes cannot be seen by the user of a database; they just help speed up queries.
- CREATE TABLE
- Creates a new table within a database.
- CREATE VIEW
- Creates a virtual table based on a saved query.
- DELETE
- Removes existing row(s) from a table. If a WHERE statement is excluded, all rows in the table will be deleted.
- FULL OUTER JOIN
- Combines rows from different tables even if the JOIN condition is not met.
- GROUP BY
- Groups a result set based on an aggregate function (COUNT(), MIN(), MAX(), SUM(), AVG()). It lists the number in each group.
- HAVING
- A conditional statement similar to WHERE but used with aggregate functions (COUNT(), MIN(), MAX(), SUM(), AVG()).
- INNER JOIN
- Returns all rows that have matching values in both tables and omits non-matching rows.
- INSERT INTO
- Creates and places new rows into a table.
- LEFT JOIN
- Combines matching rows with rows from the left-side table.
- LIMIT
- Specifies, or limits, the maximum number of rows the result set will have.
- ORDER BY
- Sorts the result set by a particular column either alphabetically or numerically.
- RIGHT JOIN
- Combines matching rows with rows from the right-side table.
- ROUND
- Rounds a value to the nearest integer or to a specific number of decimals if an optional value is provided.
- SELECT
- Every SQL query will begin with the SELECT command to fetch data from one or more tables.
- SELECT DISTINCT
- Returns unique values in the specified column(s).
- UNION
- Combines the results of two or more SELECT queries.
- UPDATE
- Edits row(s) in a table.
- WHERE
- Filters records (rows) that match a certain condition.
- WITH
- Stores the result of a query in a temporary table using an alias.
