SQL is a standardized programming language designed for managing data. It can be used for creating and updating databases as well as analyzing and integrating information from various sources.
At Mode, tables are organized by users; therefore many table names in this tutorial series will begin with user names. Tables are then grouped together under schemas identified by prefixes.
Data manipulation language
SQL is a database management language which supports many tasks including creating, altering and managing data. These activities are carried out using commands which fall under various categories like DDL, DML and TCL.
DDL commands are used to create and restructure database objects; examples are CREATE, ALTER and DROP. DML commands, however, allow us to manage actual table data – such as inserting, updating or deleting.
DML commands are used to manage access privileges of users. GRANT allows you to give privileges while REVOKE is used to revoke them. TCL commands manage transactions within databases using the COMMIT and ROLLBACK statements.
Data definition language
DDL (Data Definition Language) is a subset of SQL that defines the structure of database objects such as schemas, tables, views, sequences, catalogs, indexes, variables masks and permissions. Furthermore, DDL allows us to define fields and records within tables as well as assign field procedures directly.
DDL commands are auto-committed, meaning any changes made using them are saved permanently in the database. DDLs can be used to create, alter and drop tables, views, functions, stored procedures and triggers as well as setting data types and integrity constraints on tables.
DDL COMMENT ON is a useful way of providing descriptive text about columns or rows within a table, helping users recall its purpose more easily while simplifying queries of said table. Meanwhile, the DDL DROP TABLE command allows one to remove an entire table from a database at once.
Transaction control language
SQL databases are widely utilized by businesses for gathering and storing information. Their logical approach makes data management simpler, providing faster access to it for analysts who make smarter business decisions. Plus, their use of standard languages makes managing these databases even simpler!
Transaction control language commands such as ROLLBACK and COMMIT are essential components of SQL database administration, serving to protect the integrity and reliability of data within relational databases. They’re automatically used with DML (Data Manipulation Language) statements as part of one logical update – whether that means updating one value at once, or inserting rows across several tables.
An SQL database allows for concurrent transactions to run at once, and they should all be rolled back if one fails. Save points enable this feature for seamless reversals without losing all changes reapplied later in the transaction – perfect for fault tolerance and concurrent transactions! This feature supports recovery as well as concurrency management.
Query language
SQL is a query language commonly employed in relational databases to store, process and retrieve information. With its wide array of features designed to simplify data management for businesses and analysts alike, as well as its structured format that makes searching and discovering insights simpler than ever.
There are four basic kinds of SQL commands, namely DDL, DML, DCL and Query. DDL commands are used to define database objects like tables and users; DML are data manipulation commands while DCL manage security whereas the SELECT command allows data to be extracted from tables as well as being combined from two different tables with UNION/JOIN features.
ANSI SQL is widely implemented in commercial closed-source databases, yet it does have limitations. For instance, many implementations do not support DATE and TIME data types – therefore it is crucial that users understand its inner workings before employing it.