SQL is one of the essential programming languages out there. Learn how to code in SQL today!
SQL stands for Structured Query Language. Programmers use it to create databases that store information; this language is also used to write queries against those databases.
SQL is a database query language developed by IBM in the 1970s, and it was designed to allow users to access data stored in relational databases.
SQL is used to store and retrieve data from a database. This means it allows you to search through large amounts of data quickly and easily. You can use SQL to write programs that interact with databases, allowing you to add new records, delete existing ones, update them, and so much more.
SQL is an acronym for Structured Query Language. It is a language designed to allow users to query databases. In other words, it lets you ask questions of a database and receive answers. SQL has two main parts; the first part is called the SELECT statement. This tells the database what kind of information you would like returned. The second part is the WHERE clause. This specifies where the results should come from.
Data Types are used to define the format of data stored in a table. They are also used to determine how the computer will interpret the data.
A SQL statement is a command that tells the database what to do with the data. It consists of three parts: SELECT, FROM, and WHERE.
SELECT – This part specifies what data should be retrieved from the database.
FROM – This part specifies where the data comes from.
WHERE – This part specifies what kind of data we are looking for.
ADD -- Adds a new column to an existing table
ADD CONSTRAINT -- Creates a new constraint on an existing table, which is used to specify rules for any data in the table.
ALTER TABLE -- Adds, deletes or edits columns in a table. It can also be used to add and delete constraints in a table, as per the above.
ALTER COLUMN -- Changes the data type of a table’s column.
ALL -- Returns true if all of the subquery values meet the passed condition.
AND -- Used to join separate conditions within a WHERE clause.
ANY -- Returns true if any of the subquery values meet the given condition.
AS -- Renames a table or column with an alias value which only exists for the duration of the query.
ASC -- Used with ORDER BY to return the data in ascending order.
BETWEEN -- Selects values within the given range.
CASE -- Changes query output depending on conditions.
CHECK -- Adds a constraint that limits the value which can be added to a column.
CREATE DATABASE -- Creates a new database.
CREATE TABLE -- Creates a new table.
DEFAULT -- Sets a default value for a column
DELETE -- Delete data from a table.
DESC -- Used with ORDER BY to return the data in descending order.
DROP COLUMN -- Deletes a column from a table.
DROP DATABASE -- Deletes the entire database.
DROP DEAFULT -- Removes a default value for a column.
DROP TABLE -- Deletes a table from a database.
EXISTS -- Checks for the existence of any record within the subquery, returning true if one or more records are returned.
FROM -- Specifies which table to select or delete data from.
IN -- Used alongside a WHERE clause as a shorthand for multiple OR conditions.
INSERT INTO -- Adds new rows to a table.
IS NULL -- Tests for empty (NULL) values.
IS NOT NULL -- The reverse of NULL. Tests for values that aren’t empty / NULL.
LIKE -- Returns true if the operand value matches a pattern.
NOT -- Returns true if a record DOESN’T meet the condition.
OR -- Used alongside WHERE to include data when either condition is true.
ORDER BY -- Used to sort the result data in ascending (default) or descending order through the use of ASC or DESC keywords.
ROWNUM -- Returns results where the row number meets the passed condition.
SELECT -- Used to select data from a database, which is then returned in a results set.
SELECT DISTINCT -- Sames as SELECT, except duplicate values are excluded.
SELECT INTO -- Copies data from one table and inserts it into another.
SELECT TOP -- Allows you to return a set number of records to return from a table.
SET -- Used alongside UPDATE to update existing data in a table.
SOME -- Identical to ANY.
TOP -- Used alongside SELECT to return a set number of records from a table.
TRUNCATE TABLE -- Similar to DROP, but instead of deleting the table and its data, this deletes only the data.
UNION -- Combines the results from 2 or more SELECT statements and returns only distinct values.
UNION ALL -- The same as UNION, but includes duplicate values.
UNIQUE -- This constraint ensures all values in a column are unique.
UPDATE -- Updates existing data in a table.
VALUES -- Used alongside the INSERT INTO keyword to add new values to a table.
WHERE -- Filters results to only include data which meets the given condition.
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