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Constraints are rules applied to table columns to restrict the data that can be stored. Their purpose is to ensure data correctness, validity, and integrity within the database. Categories of Constraints NOT NULL: Ensures a column cannot have a NULL value. UNIQUE: Guarantees that all values in a column are different. PRIMARY KEY: Uniquely iden ...

Creating Tables To build a table, use the standard CREATE TABLE syntax. Separate column definitions with commas, and designate a primary key to uniquely identify each row. CREATE TABLE table_name( column_name data_type, column_name data_type, column_name data_type, column_name data_type, column_name data_type ) ENGINE = stor ...

Data Types in MySQL MySQL supports various data types organized into several categories: Category Examples Integer Types TINYINT, SMALINT, MEDIUMINT, INT, BIGINT Floating Point FLOAT, DOUBLE Decimal Numbers DECIMAL Bit Types BIT Date/Time Types YEAR, TIME, DATE, DATETIME, TIMESTAMP String Types CHAR, VARCHAR, TINYTEXT, TEXT, ME ...

Table Creation and Data Types Table creation falls under DDL statements. Each database contains structural files for its tables: SHOW TABLES; Display table structure: DESCRIBE table_name; SHOW COLUMNS FROM table_name; Field Types Integer Types TINYINT (1 byte) SMALLINT (2 bytes) MEDIUMINT (3 bytes) INT (4 bytes) BIGINT (8 bytes) Decimal Typ ...

Data Types Various data types serve specific purposes within SQL Server. Each type has defined ranges and applications for optimal use. Server Configuration Server Properties via SERVERPROPERTY Retrieve server information using the SERVERPROPERTY function: SELECT CONVERT(sysname, SERVERPROPERTY('servername')); System Views for Server Details Q ...

Sorting Query Results The ORDER BY clause controls how rows are returned. It does not alter the stored data, only the presentation. SELECT column_list FROM table_name WHERE condition ORDER BY column1 [ASC|DESC], column2 [ASC|DESC]; Single‑column ordering Sort employees by age in descending order: SELECT name, age FROM employees ORDER BY age DE ...

Database Constraints in DaMeng What Are Constraints? Constraints are rules enforced on table columns to insure data integrity. They guarantee both accuracy and validity of stored data. Constraint Types Primary Key Constraint A primary key uniquely identifies each row in a table. This field must contain unique, non-null values. Creating a table ...