Control Structures of PL/SQL Control structures are probably the most useful (and important) part of PL/pgSQL.With PL/pgSQL's control structures, you can manipulate PostgreSQL data in a very flexible and powerful way. 1.Returning From a Function RETU…

IF条件 declare cursor s is            select version from city_server t;   s_ city_server.version%type; begin   open s;   fetch s into s_;         if s_>2            then         DBMS_OUTPUT.put_line(s_);         end if;   close s; end; LOOP循环 declare …

1 PL/pgSQL Under the Hood This part discusses some implementation details that are frequently important for PL/pgSQL users to know. 1.1 Variable Substitution SQL statements and expressions within a PL/pgSQL function can refer to variables and paramet…

Cursors Rather than executing a whole query at once, it is possible to set up a cursor that encapsulates the query, and then read the query result a few rows at a time. A more interesting usage is to return a reference to a cursor that a function has…

1.Structure of PL/pgSQL The structure of PL/pgSQL is like below: [ <<label>> ] [ DECLARE declarations ] BEGIN statements END [ label ]; A label is only needed if you want to identify the block for use in an EXIT statement, or to qualify the na…

Trigger Procedures PL/pgSQL can be used to define trigger procedures on data changes or database events. A trigger procedure is created with the CREATE FUNCTION command, declaring it as a function with no arguments and a return type of trigger (for d…

Errors and Messages 1. Reporting Errors and Messages Use the RAISE statement to report messages and raise errors. RAISE [ level ] 'format' [, expression [, ... ]] [ USING option = expression [, ... ] ]; RAISE [ level ] condition_name [ USING option =…

资料1 -- Created on 2014/8/20  declare    -- Local variables here   i integer; begin   i := 12;   -- Test statements here   DBMS_OUTPUT.put_line(i); end; 资料2 declare    cursor s is            select * from city_app.city_server;   s_ s%rowtype; begin  …

<SQL必知必会>学习笔记(二) 咱们接着上一篇的内容继续.这一篇主要回顾子查询,联合查询,复制表这三类内容. 上一部分基本上都是简单的Select查询,即从单个数据库表中检索数据的单条语句,但是实际应用中的业务逻辑往往会非常复杂,所以会用到一些比较复杂的查询,如子查询,联合查询. 1.子查询 当一个查询是另一个查询的条件时,称为子查询.但是说到子查询又不的不说它与嵌套查询两者的区别,下面一张图来说明 下面再用一条sql语句来说明他们的关系. 其中在查询中又分为嵌套子查询和相关子查询,他们之间…

Django学习笔记二 模型类,字段,选项,查询,关联,聚合函数,管理器, 一 字段属性和选项 1.1 模型类属性命名限制 1)不能是python的保留关键字. 2)不允许使用连续的下划线,这是由django的查询方式决定的. 3)定义属性时需要指定字段类型,通过字段类型的参数指定选项,语法如下: 属性名=models.字段类型(选项) 1.2 字段的类型 使用时需要引入django.db.models包,字段类型如下: 类型 描述 AutoField 自动增长的IntegerField,通常不…