database

Database knowledges

Reference

  • DDL is Data Definition Language (DDL) statements are used to define the database
    structure or schema. Some examples:

    CREATE - to create table in the database
    ALTER - alters the structure of the database
    DROP - delete objects from the database
    TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed
    COMMENT - add comments to the data dictionary
    RENAME - rename an object

  • DML is Data Manipulation Language (DML) statements are used to managing data
    with schema objects. Some examples:

    SELECT - retrieve data from the a database
    INSERT - insert data into a table
    UPDATE - updates existing data within a table
    DELETE - deletes all records from a table, the space for the records remain
    MERGE - UPSERT operation (insert or update)
    CALL - call a PL/SQL or Java subprogram
    EXPLAIN PLAN - explain access path to data
    LOCK TABLE - control concurrency

  • DCL is Data Control Language (DCL) statements.

  • TCL is Transaction Control Language (DCL) statements.

事务

  • ACID
    • Atomic 原子性
    • Con 一致性
    • Isolation 隔离性
    • D 持久性
  • 并发场景
    • 脏读:
    • 不可重复读
    • 幻读

Index

  • structure
    • B-/B+ tree

Reference