Delete ALL rows from the table class101! Beware that there is NO UNDO! +-+-+-+ DELETE - SYNTAX DELETE FROM tableName WHERE criteria - EXAMPLES

If two rows have the same gpa, order by name in ascending order. Order the result by gpa in descending order. SELECT * FROM class101 WHERE gpa > 4 AND name LIKE 'k%' ORDER BY gpa DESC, name ASC - Use AND, OR, NOT to combine simple conditions. wildcard _ matches one (any) character. wildcard % matches zero or more (any) characters SELECT name FROM class101 WHERE name LIKE 'k%' - Use 'LIKE' to perform pattern-matching on strings, with SELECT name, gpa FROM class101 WHERE name = 'Tan Ah Teck' - Perform FULL-match on strings (= or !=). You can compare numbers (INT, FLOAT) using =, >, =, (!=) SELECT name, gpa FROM class101 WHERE gpa >= 4.7 - Select columns name and gpa from table class101, where the rows meet the criterion (gpa >= 4.7). The wildcard * denotes all the columns. SELECT * FROM class101 - Select ALL columns from table class101. FROM tableName WHERE criteria SELECT * FROM tableName WHERE criteria - EXAMPLES SELECT name, gpa FROM class101 - Select columns name and gpa from table class101. SQL (Structure Query Language) defines a set of intuitive commands (such as SELECT, INSERT, DELETE, UPDATE) to interact with relational database system. | id (INT) | name (VARCHAR(50)) | gpa (FLOAT) | We choose: INT (integer) for column id, VARCHAR(50) (variable-length string of up to 50 characters) for name, and FLOAT (floating-point number) for gpa. Suppose we have a database called studentdb, a table called class101 in the database with 3 columns ( id, name, gpa) and 4 rows as illustrated below. A table have rows (or records) and columns (or fields).

A relational database system contains many databases.

SQL By ExamplesĪ relational database system organizes data in the following hierarchy: However, most of the database vendors have their own directs, e.g., PL/SQL (Oracle), Transact-SQL (Microsoft, SAP), PL/pgSQL (PostgreSQL). SQL, one of the earlier programming language, was subsequently developed by Donald D. Codd of IBM proposed the Relational Database Model in 1970. SQL defines a set of commands, such as SELECT, INSERT, UPDATE, DELETE, CREATE TABLE, DROP TABLE, and etc.Įdgar F.

the open-source MySQL, PostgreSQL, mariaDB, Embedded Apache Derby (Java DB), mSQL (mini-SQL), SQLite, Apache OpenOffice's Base, and mongoDB (non-relational).Ī high-level programming language, called Structure Query Language (SQL), is designed for interacting with the relational databases.

the commercial Oracle, IBM DB2, Microsoft SQL Server and Access, SAP Hana.Popular Relationship Database Management System (RDBMS) includes: Tables are related based on common columns to eliminate data redundancy and ensure data integrity. A table has rows (or records) and columns (or fields). This article is applicable to MySQL 8.0, which is the successor of MySQL 5.7, where 5 was dropped?! Introduction to Relational Database and SQL Relational DatabasesĪ relational database organizes data in tables.

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