Explain types of tables in oracle

本文介绍了Oracle数据库中几种主要的表类型,包括堆组织表、对象表、索引组织表、哈希集群表、嵌套表及索引集群表等,并详细解释了每种表类型的特性及其适用场景。

In Oracle, tables are the basic storage units. There are several types of database tables. Different types of tables have different characteristics.

Heap Organized Table:

The default table type in Oracle is heap table. If you use “create table” clause normally, you create a standard database table. Exp:

create table A
(
x char
);

Object Table

This type of table is created based on an object type and not collection of columns. It is usually used in special cases. The logic depends on object-oriented programming. “create table ” statement for object tables is:

create table test of x_type;

create or replace type atype
as object
(
a varchar2(30),
b date
)

Create table p of atype;

Index Organized Tables

Index Organized Tables have their primary key and non-key column data stored within the same B-Tree structure.

The data is stored within the primary key index.

Use:

IOTs make accessing data via the primary key quicker as the key and the data reside in the same structure.
Since there is no need to read an index, the table data is read in a separate structure.
Less duplication of the key columns in an index and table mean low storage requirements.

Hash clustered tables

Hash clusters provide a good facility for storage and retrieval.

In the case of a heap table, the rows are not sorted in a user-controlled manner.

Oracle hash cluster tables can improve random row access speed by foour times as the hash can get the row location far faster than index access.

Multiple table hash clusters store logically-related rows on a single data block due to which you can access a whole unit of data in a single physical I/O.

Nested tables

Nested table can be used to link the subordinate data items to the base table using the object ID (OID).

Oracle objects can be directly referenced by using pointers as opposed joining relational.

Objects in standard relational databases need to be reassembled every time it is used.

Index cluster tables

An index cluster uses an index to maintain row sequence.

A table cluster is a group of tables that share the same data blocks, since they share common columns and are often used together.

All rows for each table are stored in the same data blocks, When you create cluster tables are created.

The cluster key value is the value of the cluster key columns for a particular row.

Index cluster tables can be either multi-table or single-table

""" title: SQL Server Access author: MENG author_urls: - https://github.com/mengvision description: A tool for reading database information and executing SQL queries, supporting multiple databases such as MySQL, PostgreSQL, SQLite, and Oracle. It provides functionalities for listing all tables, describing table schemas, and returning query results in CSV format. A versatile DB Agent for seamless database interactions. required_open_webui_version: 0.5.4 requirements: pymysql, sqlalchemy, cx_Oracle version: 0.1.6 licence: MIT # Changelog ## [0.1.6] - 2025-03-11 ### Added - Added `get_table_indexes` method to retrieve index information for a specific table, supporting MySQL, PostgreSQL, SQLite, and Oracle. - Enhanced metadata capabilities by providing detailed index descriptions (e.g., index name, columns, and type). - Improved documentation to include the new `get_table_indexes` method and its usage examples. - Updated error handling in `get_table_indexes` to provide more detailed feedback for unsupported database types. ## [0.1.5] - 2025-01-20 ### Changed - Updated `list_all_tables` and `table_data_schema` methods to accept `db_name` as a function parameter instead of using `self.valves.db_name`. - Improved flexibility by decoupling database name from class variables, allowing dynamic database selection at runtime. ## [0.1.4] - 2025-01-17 ### Added - Added support for Oracle database using `cx_Oracle` driver. - Added dynamic engine creation in each method to ensure fresh database connections for every operation. - Added support for Oracle-specific queries in `list_all_tables` and `table_data_schema` methods. ### Changed - Moved `self._get_engine()` from `__init__` to individual methods for better flexibility and tool compatibility. - Updated `_get_engine` method to support Oracle database connection URL. - Improved `table_data_schema` method to handle Oracle-specific column metadata. ### Fixed - Fixed potential connection issues by ensuring each method creates its own database engine. - Improved error handling for Oracle-specific queries and edge cases. ## [0.1.3] - 2025-01-17 ### Added - Added support for multiple database types (e.g., MySQL, PostgreSQL, SQLite) using SQLAlchemy. - Added configuration flexibility through environment variables or external configuration files. - Enhanced query security with stricter validation and SQL injection prevention. - Improved error handling with detailed exception messages for better debugging. ### Changed - Replaced `pymysql` with SQLAlchemy for broader database compatibility. - Abstracted database connection logic into a reusable `_get_engine` method. - Updated `table_data_schema` method to support multiple database types. ### Fixed - Fixed potential SQL injection vulnerabilities in query execution. - Improved handling of edge cases in query validation and execution. ## [0.1.2] - 2025-01-16 ### Added - Added support for specifying the database port with a default value of `3306`. - Abstracted database connection logic into a reusable `_get_connection` method. ## [0.1.1] - 2025-01-16 ### Added - Support for additional read-only query types: `SHOW`, `DESCRIBE`, `EXPLAIN`, and `USE`. - Enhanced query validation to block sensitive keywords (e.g., `INSERT`, `UPDATE`, `DELETE`, `CREATE`, `DROP`, `ALTER`). ### Fixed - Improved handling of queries starting with `WITH` (CTE queries). - Fixed case sensitivity issues in query validation. ## [0.1.0] - 2025-01-09 ### Initial Release - Basic functionality for listing tables, describing table schemas, and executing `SELECT` queries. - Query results returned in CSV format. """ import os from typing import List, Dict, Any from pydantic import BaseModel, Field import re from sqlalchemy import create_engine, text from sqlalchemy.engine.base import Engine from sqlalchemy.exc import SQLAlchemyError class Tools: class Valves(BaseModel): db_host: str = Field( default="localhost", description="The host of the database. Replace with your own host.", ) db_user: str = Field( default="admin", description="The username for the database. Replace with your own username.", ) db_password: str = Field( default="admin", description="The password for the database. Replace with your own password.", ) db_name: str = Field( default="db", description="The name of the database. Replace with your own database name.", ) db_port: int = Field( default=3306, # Oracle 默认端口 description="The port of the database. Replace with your own port.", ) db_type: str = Field( default="mysql", description="The type of the database (e.g., mysql, postgresql, sqlite, oracle).", ) def __init__(self): """ Initialize the Tools class with the credentials for the database. """ print("Initializing database tool class") self.citation = True self.valves = Tools.Valves() def _get_engine(self) -> Engine: """ Create and return a database engine using the current configuration. """ if self.valves.db_type == "mysql": db_url = f"mysql+pymysql://{self.valves.db_user}:{self.valves.db_password}@{self.valves.db_host}:{self.valves.db_port}/{self.valves.db_name}" elif self.valves.db_type == "postgresql": db_url = f"postgresql://{self.valves.db_user}:{self.valves.db_password}@{self.valves.db_host}:{self.valves.db_port}/{self.valves.db_name}" elif self.valves.db_type == "sqlite": db_url = f"sqlite:///{self.valves.db_name}" elif self.valves.db_type == "oracle": db_url = f"oracle+cx_oracle://{self.valves.db_user}:{self.valves.db_password}@{self.valves.db_host}:{self.valves.db_port}/?service_name={self.valves.db_name}" else: raise ValueError(f"Unsupported database type: {self.valves.db_type}") return create_engine(db_url) def list_all_tables(self, db_name: str) -> str: """ List all tables in the database. :param db_name: The name of the database. :return: A string containing the names of all tables. """ print("Listing all tables in the database") engine = self._get_engine() # 动态创建引擎 try: with engine.connect() as conn: if self.valves.db_type == "mysql": result = conn.execute(text("SHOW TABLES;")) elif self.valves.db_type == "postgresql": result = conn.execute( text( "SELECT table_name FROM information_schema.tables WHERE table_schema = 'public';" ) ) elif self.valves.db_type == "sqlite": result = conn.execute( text("SELECT name FROM sqlite_master WHERE type='table';") ) elif self.valves.db_type == "oracle": result = conn.execute(text("SELECT table_name FROM user_tables;")) else: return "Unsupported database type." tables = [row[0] for row in result.fetchall()] if tables: return ( "Here is a list of all the tables in the database:\n\n" + "\n".join(tables) ) else: return "No tables found." except SQLAlchemyError as e: return f"Error listing tables: {str(e)}" def get_table_indexes(self, db_name: str, table_name: str) -> str: """ Get the indexes of a specific table in the database. :param db_name: The name of the database. :param table_name: The name of the table. :return: A string describing the indexes of the table. """ print(f"Getting indexes for table: {table_name}") engine = self._get_engine() try: key, cloumn = 0, 1 with engine.connect() as conn: if self.valves.db_type == "mysql": query = text(f"SHOW INDEX FROM {table_name}") key, cloumn = 2, 4 elif self.valves.db_type == "postgresql": query = text( """ SELECT indexname, indexdef FROM pg_indexes WHERE tablename = :table_name; """ ) elif self.valves.db_type == "sqlite": query = text( """ PRAGMA index_list(:table_name); """ ) elif self.valves.db_type == "oracle": query = text( """ SELECT index_name, column_name FROM user_ind_columns WHERE table_name = :table_name; """ ) else: return "Unsupported database type." result = conn.execute(query) indexes = result.fetchall() if not indexes: return f"No indexes found for table: {table_name}" description = f"Indexes for table '{table_name}':\n" for index in indexes: description += f"- {index[key]}: {index[cloumn]}\n" return description # result = conn.execute(query) # description = result.fetchall() # if not description: # return f"No indexes found for table: {table_name}" # column_names = result.keys() # description = f"Query executed successfully. Below is the actual result of the query {query} running against the database in CSV format:\n\n" # description += ",".join(column_names) + "\n" # for row in description: # description += ",".join(map(str, row)) + "\n" # return description except SQLAlchemyError as e: return f"Error getting indexes: {str(e)}" def table_data_schema(self, db_name: str, table_name: str) -> str: """ Describe the schema of a specific table in the database, including column comments. :param db_name: The name of the database. :param table_name: The name of the table to describe. :return: A string describing the data schema of the table. """ print(f"Database: {self.valves.db_name}") print(f"Describing table: {table_name}") engine = self._get_engine() # 动态创建引擎 try: with engine.connect() as conn: if self.valves.db_type == "mysql": query = text( " SELECT COLUMN_NAME, COLUMN_TYPE, IS_NULLABLE, COLUMN_KEY, COLUMN_COMMENT " " FROM INFORMATION_SCHEMA.COLUMNS " f" WHERE TABLE_SCHEMA = '{self.valves.db_name}' AND TABLE_NAME = '{table_name}';" ) elif self.valves.db_type == "postgresql": query = text( """ SELECT column_name, data_type, is_nullable, column_default, '' FROM information_schema.columns WHERE table_name = :table_name; """ ) elif self.valves.db_type == "sqlite": query = text("PRAGMA table_info(:table_name);") elif self.valves.db_type == "oracle": query = text( """ SELECT column_name, data_type, nullable, data_default, comments FROM user_tab_columns LEFT JOIN user_col_comments ON user_tab_columns.table_name = user_col_comments.table_name AND user_tab_columns.column_name = user_col_comments.column_name WHERE user_tab_columns.table_name = :table_name; """ ) else: return "Unsupported database type." # result = conn.execute( # query, {"db_name": db_name, "table_name": table_name} # ) result = conn.execute(query) columns = result.fetchall() if not columns: return f"No such table: {table_name}" description = ( f"Table '{table_name}' in the database has the following columns:\n" ) for column in columns: if self.valves.db_type == "sqlite": column_name, data_type, is_nullable, _, _, _ = column column_comment = "" elif self.valves.db_type == "oracle": ( column_name, data_type, is_nullable, data_default, column_comment, ) = column else: ( column_name, data_type, is_nullable, column_key, column_comment, ) = column description += f"- {column_name} ({data_type})" if is_nullable == "YES" or is_nullable == "Y": description += " [Nullable]" if column_key == "PRI": description += " [Primary Key]" if column_comment: description += f" [Comment: {column_comment}]" description += "\n" return description except SQLAlchemyError as e: return f"Error describing table: {str(e)}" def execute_read_query(self, query: str) -> str: """ Execute a read query and return the result in CSV format. :param query: The SQL query to execute. :return: A string containing the result of the query in CSV format. """ print(f"Executing query: {query}") normalized_query = query.strip().lower() if not re.match( r"^\s*(select|with|show|describe|desc|explain|use)\s", normalized_query ): return "Error: Only read-only queries (SELECT, WITH, SHOW, DESCRIBE, EXPLAIN, USE) are allowed. CREATE, DELETE, INSERT, UPDATE, DROP, and ALTER operations are not permitted." sensitive_keywords = [ "insert", "update", "delete", "create", "drop", "alter", "truncate", "grant", "revoke", "replace", ] for keyword in sensitive_keywords: if re.search(rf"\b{keyword}\b", normalized_query): return f"Error: Query contains a sensitive keyword '{keyword}'. Only read operations are allowed." engine = self._get_engine() # 动态创建引擎 try: with engine.connect() as conn: result = conn.execute(text(query)) rows = result.fetchall() if not rows: return "No data returned from query." column_names = result.keys() csv_data = f"Query executed successfully. Below is the actual result of the query {query} running against the database in CSV format:\n\n" csv_data += ",".join(column_names) + "\n" for row in rows: csv_data += ",".join(map(str, row)) + "\n" return csv_data except SQLAlchemyError as e: return f"Error executing query: {str(e)}" 将上面的工具连接到Microsoft sql server
07-23
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