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Create Insert
In Microsoft SQL Server (MSSQL), the `CREATE` statement is part of "Data Definition Language" (DDL) and is used to define and create database objects such as tables, views, indexes, and stored procedures. It allows database administrators and developers to structure and organize the database schema by specifying the properties, columns, and constraints of these objects. On the other hand, the `INSERT` statement is categorized under "Data Manipulation Language" (DML) and is used to insert new rows of data into existing tables. It facilitates the addition of specific data values into designated columns of a table, enabling applications to populate and modify the database content dynamically. Understanding these distinctions is essential for effectively managing database schema design and data manipulation tasks within MSSQL, ensuring efficient database management and application development processes.
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05:44min
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Rename
In SQL databases, the `RENAME` operation is categorized under "Data Definition Language" (DDL) and is used to modify the names of existing database objects. This operation allows database administrators and developers to change the names of tables, columns, indexes, constraints, or other database entities. Renaming is crucial for maintaining database schema integrity and improving readability in database management. For instance, renaming a table using SQL syntax involves using commands like `sp_rename` in Microsoft SQL Server or `ALTER TABLE` statements in other SQL dialects to update object names without altering their structure or data. Effective use of the `RENAME` operation helps ensure consistency and clarity in database design and management practices.
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03:02min
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NotNullUnique
In SQL databases, constraints like `NOT NULL` and `UNIQUE` are integral components of "Data Definition Language" (DDL), used to define rules for columns within database tables. The `NOT NULL` constraint ensures that a column must contain a value, preventing NULL entries. For instance, `CREATE TABLE users (user_id INT NOT NULL, username VARCHAR(50));` specifies that every row in the `users` table must have a value for `user_id`. On the other hand, the `UNIQUE` constraint ensures that all values in a column (or a combination of columns) are unique across the table. This prevents duplicate entries and enforces data integrity. For example, `CREATE TABLE products (product_id INT PRIMARY KEY, product_name VARCHAR(100) UNIQUE);` ensures that each `product_name` value in the `products` table is unique. These constraints are fundamental for maintaining data quality and consistency, ensuring accurate and reliable operations within SQL databases.
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05:18min
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Check Default
In SQL, "CHECK" and "DEFAULT" are constraints applied to columns within tables and are considered part of the "Data Definition Language" (DDL). These constraints ensure data integrity and enforce specific rules or conditions on the data stored in the database.
1. **CHECK Constraint**: This constraint ensures that the values entered into a column meet a specified condition. For example, `CHECK (age >= 18)` ensures that the `age` column in a table contains values that are 18 or greater.
2. **DEFAULT Constraint**: This constraint specifies a default value for a column when no explicit value is provided during an `INSERT` operation. For instance, `DEFAULT 'Not available'` assigns the default value 'Not available' to a column if no other value is provided.
Both constraints are defined using SQL statements such as `CREATE TABLE` or `ALTER TABLE` and are crucial for maintaining data consistency and enforcing business rules within SQL databases.
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04:26min
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Primary Key
In SQL databases, the "PRIMARY KEY" constraint is a crucial component of "Data Definition Language" (DDL) used to uniquely identify each record (row) within a table. It ensures that the values in the designated primary key column(s) are unique and not NULL, thereby enforcing entity integrity. The primary key serves as a reference point for establishing relationships between tables and facilitates efficient data retrieval through indexing. For example, defining a table with a primary key would look like this: `CREATE TABLE students (student_id INT PRIMARY KEY, student_name VARCHAR(100));` Here, `student_id` uniquely identifies each student record. Mastery of primary keys is essential for database design, data integrity maintenance, and optimizing database performance in SQL-based applications and systems.
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02:33min
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Foreign Key
In SQL databases, the "FOREIGN KEY" constraint is a critical element of "Data Definition Language" (DDL) used to establish relationships between tables. It ensures referential integrity by linking a column or set of columns in one table to the primary key or unique constraint of another table. This linkage allows enforcing relationships between related data across tables, preventing orphaned records and maintaining data consistency. For example, `FOREIGN KEY (employee_id) REFERENCES employees(id)` establishes a relationship where the `employee_id` column in one table references the `id` column in another, ensuring that every `employee_id` value exists in the referenced table. Mastery of foreign keys is crucial for designing efficient database schemas, optimizing query performance, and ensuring accurate data management in SQL-based applications and systems.
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02:43min
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Create, Later, Drop
In Microsoft SQL Server (MS SQL), operations like CREATE, ALTER, and DROP are categorized under "Data Definition Language" (DDL). These commands are used to define, modify, and delete database objects such as tables, views, indexes, and stored procedures.
CREATE: The CREATE statement is used to create new database objects. For example, CREATE TABLE, CREATE INDEX, CREATE VIEW, etc., are used to define tables, indexes, and views respectively.
ALTER: The ALTER statement is used to modify existing database objects without dropping and recreating them entirely. For example, ALTER TABLE, ALTER VIEW, etc., are used to modify the structure of tables and views.
DROP: The DROP statement is used to delete existing database objects. For example, DROP TABLE, DROP VIEW, etc., are used to remove tables, views, and other objects from the database.
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05:20min
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