Oracle

having count with join

由 丶灬走出姿态 提交于 2021-02-09 11:45:49
问题 I want to find out which playlist have more than 2 songs. The statement works but I want the name of the playlist and the count() for the songs displayed. I think i have to use a join but I didn't get it how this should work. Can someone helps please? playlist table ++++++++++++++ id name playlist_songs table ++++++++++++++++++++ song_id playlist_id SELECT p.name FROM playlist p WHERE p.id in (SELECT s.playlist_id counter FROM playlist_songs s group by playlist_id having count(song_id)>2);

having count with join

由 久未见 提交于 2021-02-09 11:45:15
问题 I want to find out which playlist have more than 2 songs. The statement works but I want the name of the playlist and the count() for the songs displayed. I think i have to use a join but I didn't get it how this should work. Can someone helps please? playlist table ++++++++++++++ id name playlist_songs table ++++++++++++++++++++ song_id playlist_id SELECT p.name FROM playlist p WHERE p.id in (SELECT s.playlist_id counter FROM playlist_songs s group by playlist_id having count(song_id)>2);

Retrieve large clob data using sqlplus

由 帅比萌擦擦* 提交于 2021-02-09 10:51:46
问题 How to completely retrieve large clob data from a table using sqlplus to the stdout? There is a way to get it completely using language specific DB APIs. But when I try to get it using purely sqlplus, I've faced several problems such as, Output buffer is too small (4000 is max) Character string buffer too small Since oracle clob fields can contain 4GB (max) of data, is there any correct way to get the complete data chunk using sqlplus? Can I download it as a file? I hope that the question is

mysql基础语句

由 送分小仙女□ 提交于 2021-02-09 10:05:28
转载自： http://blog.csdn.net/u011001084/article/details/51318434 一、关系型数据库和SQL 实际上准确的讲，SQL是一门语言，而不是一个数据库。 什么是SQL呢？简而言之，SQL就是维护和使用关系型数据库中的的数据的一种标准的计算机语言。 1.1 SQL语言主要有3个主要的组成部分。 DML(Data Manipulation Language)数据操纵语言。这个模块可以让我们检索、修改、增加、删除数据库中的数据。 DDL(Data Definition Language)数据定义语言。是的我们能够创建和修改数据库本身。如：DDL提供 ALTER 语句，他让我们可以修改数据库中表的设计。 DCL(Data Control Language)数据控制语言，用于维护数据库的安全。 在SQL术语中，记录(record)和字段(field)实际上就称为行(row)和列(column)。 1.2 主键和外键 主键之所以有必要： 首先使你唯一标识表中单独的一行。主键确保了唯一性。 可以很容易的将一个表和另一个表关联。 主键一般就会自动默认创建索引，提高了查询速度。 外键就是说A表中的某个字段，同时是B中的主键，那么这个字段就是A表中的外键。希望A表中的这个外键的值必须是B中已经存在的值。 1.3 数据类型 一般来讲，有3中重要的数据类型

C# 连接Oracle数据库，免安装oracle客户端

由 谁说我不能喝 提交于 2021-02-09 08:46:23
一、方案1 首先下面的内容，有待我的进一步测试和证实。18.12.20 被证实了，还需要安装Oracle客户端，或者本机上安装oracle数据库软件。 18.12.20 1.下载Oracle.ManagedDataAccess.dll 2.添加到C#引用 3.命名空间引用 using Oracle.ManagedDataAccess.Client; 4. 连接参数的获取 然后 打开Oracle安装的文件夹 ，以Oracle10为例D:\Oracle10\NETWORK\ADMIN\tnsnames.ora,打开这个文件，会看到 如果没有请按照图片内容输入即可，host=[主机名称],SERVICE_NAME=[随意取] 5.完成上述后，连接字符串： strConnection = “Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=LocalHost)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=orcl)));Persist Security Info=True;User ID=XXXX;Password=XXXX;”； 简单说明一下这个连接字符串，HOST=LostHost|127.0.0.1|主机名三者均可，选择一个就行； SERVICE_NAME=

Linux关闭透明大页配置

由 孤人 提交于 2021-02-09 07:42:57
一、为何要关闭透明大页 A--MOS获取 . #翻译 由于透明超大页面已知会导致意外的节点重新启动并导致RAC出现性能问题，因此Oracle强烈建议禁用透明超大页面。 另外，即使在单实例数据库环境中，透明超大页面也可能会导致问题，并出现意外的性能问题或延迟。 因此，Oracle建议在运行Oracle的所有数据库服务器上禁用透明超大页面 #原版： Because Transparent HugePages are known to cause unexpected node reboots and performance problems with RAC, Oracle strongly advises to disable the use of Transparent HugePages. In addition, Transparent Hugepages may cause problems even in a single-instance database environment with unexpected performance problems or delays. As such, Oracle recommends disabling Transparent HugePages on all Database servers running Oracle B-

How to return only latest record on join [duplicate]

由 ℡╲_俬逩灬. 提交于 2021-02-09 02:45:37
问题 This question already has answers here : Fetch the row which has the Max value for a column (35 answers) Closed 5 years ago . I'm joining tables. I only want to return one record from the joining table, based on a date field. Here's a simplified fiddle of what I've done so far: http://sqlfiddle.com/#!3/be0cdd/2 My tables: CUSTOMER | CustomerID | -------------- | 1 | PURCHASE | PurchaseID | CustomerID | ProductID | CreateDate | ArchiveFlag | ----------------------------------------------------

初识数据库MySQL

由 ≯℡__Kan透↙ 提交于 2021-02-09 00:02:00
一、认识数据库 1：什么是数据（Data） 　　　描述事物的符号记录被称为数据，这个符号可以是数字，文字，图片，声音，语言等 2：什么是数据库（DataBase,简称DB） 　　 数据库是存放数据的仓库，库一般存放在计算机存储设备上，而数据是按一定的格式存放的 3：什么是数据库管理系统（DataBase Mangement System简称：DBMS） 　　 关系型数据：数据与数据之间可以有关联和限制的；关系型的数据库通常都是表结构，也就是意味着你在用关系型数据的时候 　　非关系型数据库：是以key-value存储的，没有表结构 关系型：如：sqllite,db2,oracle,access,sq1 sever,MySQL, 注意：sql语句通用 非关系型：mongodb(文档型数据，非常接近关系型的非关系型数据), redis, memcache 二、初识MySQL 　　1、MySQL是一个关系型数据库管理系统，由瑞典MySQL AB 公司开发，目前属于 Oracle 旗下公司 mysql是什么？ 　　 就是一个基于socket(套接字)编写的c/s架构的软件，本质就是一款基于网络通信的应用软件　 服务端 -基于socket通信 -收发消息 -SQL语句(是一个公共的标准) 客户端 -基于socket通信 -收发消息 -SQL语句 ps:MySQL

Use for loop after the With Clause in PL/SQL

由 泄露秘密 提交于 2021-02-08 15:46:05
问题 Im using PL/SQL. I am trying to have a for loop right after I define my temporary tables in the with clause. However, Im getting an error to have a SELECT query first. For instance WITH TMP1 AS (.....), TMP2 AS (......), TMP3 AS (......) FOR R IN (SELECT DISTINCT ..... FROM TMP1 WHERE .....) LOOP SELECT .... FROM TMP2, TMP2 WHERE TMP2.... = R..... .... How do I go about doing so? Thanks 回答1: You can't access a CTE outside of the whole statement. And you can't access individual parts of a CTE

Oracle: Difference between non-pooled connections and DRCP

由 风格不统一 提交于 2021-02-08 15:00:35
问题 I am actually reading Oracle-cx_Oracle tutorial. There I came across non-pooled connections and DRCP, Basically I am not a DBA so I searched with google but couldn't found any thing. So could somebody help me understand what are they and how they are different to each other. Thank you. 回答1: Web tier and mid-tier applications typically have many threads of execution, which take turns using RDBMS resources. Currently, multi-threaded applications can share connections to the database efficiently
订阅 Oracle