Oracle纵向表转换为横向表写法
Oracle纵向表转换为横向表写法 假设存在如下纵向表,第一列为id(可能是某个业务数据的id),第二列为类型,第三列为类型对应的值
Oracle纵向表转换为横向表写法
假设存在如下纵向表,第一列为id(可能是某个业务数据的id),第二列为类型,第三列为类型对应的值,如下图:
如上表,存在2,3,4三种类型,其中业务数据ID为1的三种类型都有值,业务数据ID为2的三种类型都有值,业务数据ID为3的只有类型2和3有值,现在要把纵向表横过来显示,可以采用如下代码:
-- =========================================================
-- 纵向表变横向表:
-- 1. 转换类型,类型的值必须是整数,且不等于0,即0没有意义,0可以表示为空
-- =========================================================
SELECT
t.id,
SUM(DECODE(t.code, 2, 2, 0)) "第二项", -- 如果该行类型为2则就是2,其它的都为0
SUM(DECODE(t.code, 3, 3, 0)) "第三项",
SUM(decode(t.code, 4, 4, 0)) "第四项"
FROM ttt t WHERE t.id=1 GROUP BY t.id;
-- =========================================================
-- 纵向表变横向表:
-- 1. 转换类型对应的数据,且数据需要是数值,且0没有意义,,即0可以表示为空
-- =========================================================
SELECT
t.id,
SUM(DECODE(t.code, 2, t.val, 0)) "第二项", -- 如果该行类型为2则显示2类型对应的值DECODE,否则都显示0
SUM(DECODE(t.code, 3, t.val, 0)) "第三项",
SUM(DECODE(t.code, 4, t.val, 0)) "第四项"
FROM ttt t GROUP BY t.id;

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics



Full table scanning may be faster in MySQL than using indexes. Specific cases include: 1) the data volume is small; 2) when the query returns a large amount of data; 3) when the index column is not highly selective; 4) when the complex query. By analyzing query plans, optimizing indexes, avoiding over-index and regularly maintaining tables, you can make the best choices in practical applications.

Yes, MySQL can be installed on Windows 7, and although Microsoft has stopped supporting Windows 7, MySQL is still compatible with it. However, the following points should be noted during the installation process: Download the MySQL installer for Windows. Select the appropriate version of MySQL (community or enterprise). Select the appropriate installation directory and character set during the installation process. Set the root user password and keep it properly. Connect to the database for testing. Note the compatibility and security issues on Windows 7, and it is recommended to upgrade to a supported operating system.

InnoDB's full-text search capabilities are very powerful, which can significantly improve database query efficiency and ability to process large amounts of text data. 1) InnoDB implements full-text search through inverted indexing, supporting basic and advanced search queries. 2) Use MATCH and AGAINST keywords to search, support Boolean mode and phrase search. 3) Optimization methods include using word segmentation technology, periodic rebuilding of indexes and adjusting cache size to improve performance and accuracy.

The difference between clustered index and non-clustered index is: 1. Clustered index stores data rows in the index structure, which is suitable for querying by primary key and range. 2. The non-clustered index stores index key values and pointers to data rows, and is suitable for non-primary key column queries.

Article discusses popular MySQL GUI tools like MySQL Workbench and phpMyAdmin, comparing their features and suitability for beginners and advanced users.[159 characters]

Article discusses strategies for handling large datasets in MySQL, including partitioning, sharding, indexing, and query optimization.

MySQL is an open source relational database management system. 1) Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2) Basic operations: INSERT, UPDATE, DELETE and SELECT. 3) Advanced operations: JOIN, subquery and transaction processing. 4) Debugging skills: Check syntax, data type and permissions. 5) Optimization suggestions: Use indexes, avoid SELECT* and use transactions.

In MySQL database, the relationship between the user and the database is defined by permissions and tables. The user has a username and password to access the database. Permissions are granted through the GRANT command, while the table is created by the CREATE TABLE command. To establish a relationship between a user and a database, you need to create a database, create a user, and then grant permissions.
