SQL

Numeric

A common SQL data type used for storing numerical values.

Date/Time

A SQL data type for storing dates and times.

String

A SQL data type used for storing text.

Boolean

A data type that can hold one of two values: true or false.

SELECT statement

Used to retrieve data from one or more tables in a database.

FROM

Identifies the table from which to retrieve data.

Primary Key

A unique identifier for each row in a table which ensures no duplicate or NULL values.

Foreign Key

Links a column in one table to the primary key column in another table for data integrity.

FULL OUTER JOIN

Returns all rows from both tables.

INNER JOIN

Returns matching rows from both tables.

LEFT JOIN

Returns all rows from the left table and matching rows from the right table; NULL for non-matching.

RIGHT JOIN

Returns all rows from the right table and matching rows from the left table; NULL for non-matching.

CROSS JOIN

Returns all possible combinations of rows from both tables.

OUTER JOIN

Returns all rows from both tables, filling missing values with NULL.

Self-join

A query where a table is joined with itself, useful for hierarchical data.

UNION

Combines results of two SELECT statements and removes duplicates.

UNION ALL

Combines results of two SELECT statements and includes all rows, even duplicates.

WHERE

Filters rows before aggregation.

GROUP BY

Groups rows into summary rows based on column values.

HAVING

Filters records after aggregation.

ORDER BY

Sorts rows in ascending or descending order.

DISTINCT

Removes duplicate values from the result set and ensures only unique values are returned

Subquery

A nested query inside another query.

LIMIT

Restricts the number of rows returned.

RANK ()

Assigns a unique rank to each row, skipping ranks for duplicates.

DENSE_RANK()

Assigns ranks without skipping numbers for duplicates.

BETWEEN

Filters data within an inclusive range.

NULL

Represents missing data in SQL.

IS NULL

Identifies where a column has missing data.

IS NOT NULL

Filters out rows that do not have missing data.

COALESCE ()

Replaces NULL values in queries to prevent calculation errors.

SUM()

Adds up all values in a column.

AVG()

Calculates the average value of a specified column.

COUNT()

Counts the number of rows in a result set.

MIN()

Returns the smallest value in a column.

MAX()

Returns the largest value in a column.

DELETE

Removes specific rows from a table with rollback capability.

TRUNCATE

Quickly removes all records from a table, keeping the structure, cannot be rolled back.

DROP

Permanently deletes the entire table from the database, cannot be rolled back.

FULL OUTER JOIN

Returns all rows from both tables, including rows with no matches.

INNER JOIN

Retrieves only the rows that have matching values in both tables, filtering out non-matching records.

LEFT JOIN

Returns all records from the left table and matching records from the right table; returns NULL for right table columns with no match.

RIGHT JOIN

Returns all records from the right table and matching records from the left table; returns NULL for left table columns with no match.

CROSS JOIN

Produces a Cartesian product, returning all possible combinations of rows from both tables.

UNION

Combines the results of two or more SELECT statements into a single result set, removing duplicate records.

WHERE

Filters rows before any aggregation occurs, i.e., before applying GROUP BY.

GROUP BY

Groups rows sharing a specified column value into summary rows, useful for aggregation.

HAVING

Filters records after aggregation has been performed.

ORDER BY

Sorts the results set in ascending (default) or descending order based on one or more columns.

DISTINCT

Removes duplicates from the result set, ensuring all returned values are unique.

NULL

Represents absent or missing data in SQL.

COALESCE()

A function that takes a list of values and returns the first non-NULL value, useful for replacing NULL in queries.

SUM()

Calculates the total sum of a numerical column.

AVG()

Computes the average of a numerical column.

COUNT()

Counts the number of rows or non-NULL values in a column.

MIN()

Returns the smallest value in a specified column.

MAX()

Returns the largest value in a specified column.

DELETE

Used to remove specific rows from a table while allowing for rollback if needed.

TRUNCATE

Efficiently removes all records from a table but retains the table structure; cannot be rolled back.

DROP

Permanently deletes an entire table from the database, including its structure and data; cannot be undone.