Knowledge base
SQL guides
How-tos and concepts from the historical openquery.com URL inventory — linked for discovery and crawl paths.
How-to
Practical SQL tasks.
How To Use Distinct In SQL
Use DISTINCT to return unique records, including multi-column and NULL examples.
How To Write SQL Queries
How to write SQL queries for relational databases.
How to Create A Table In SQL
CREATE TABLE: columns, types, and constraints.
How To Create A Table In SQL
Historical duplicate URL for creating tables in SQL.
How To Insert Data Into SQL
Insert rows into tables with SQL.
How To Delete A Table In SQL
Drop or clear tables with SQL.
How To Drop A Column In SQL
Remove a column from a table with ALTER TABLE … DROP COLUMN.
How To Remove Duplicates In SQL
Find and remove duplicate rows in SQL.
How Can We Get The Number Of Records Or Rows In A Table Using MySQL
Count rows in a MySQL table.
How Is SQL Used?
Common ways SQL is used with relational databases.
How Long Does It Take To Learn SQL?
What to expect when learning SQL.
Is SQL Hard To Learn?
Difficulty of learning SQL for beginners.
Is Not Null In SQL
IS NOT NULL and three-valued logic in SQL.
Can A Foreign Key Be A Primary Key?
When a foreign key column is also a primary key.
Concepts
Definitions and building blocks.
What Is SQL?
Structured Query Language for relational databases.
What Does SQL Stand For?
SQL = Structured Query Language.
What Is SQL Used For?
What SQL is used for in applications and analytics.
What Is SQL Server?
Microsoft SQL Server overview.
What Is DDL?
Data Definition Language: CREATE, ALTER, DROP, TRUNCATE.
What Does Alter Mean?
ALTER statements for changing schema objects.
What Does Collate Mean?
Collations and string comparison in SQL.
What Is A Primary Key?
Primary keys uniquely identify rows.
What Is Primary Key?
Primary key basics.
What Is The Purpose Of The Primary Key?
Why tables need a primary key.
What Is A Foreign Key In Database?
Foreign keys and referential integrity.
What Is A Query In SQL?
SQL queries and SELECT.
What Is A Query In Database?
What a database query is.
What Is Inner Join In SQL?
INNER JOIN matching rows from both tables.
What Is A View In SQL?
SQL views as stored queries.
What Is A Trigger In SQL?
Triggers that fire on table changes.
What Is A Snapshot SQL?
Snapshots in SQL and database contexts.
What Is A Dimension SQL?
Dimensions in analytical SQL models.
What Is Rank?
RANK and related window functions.
What Is Percentile Rank?
Percentile rank in SQL.
What Is RDS?
Amazon RDS managed relational databases.
What Is MDS?
MDS on macOS — Spotlight metadata server.