sqlite 生成的列依赖表达式

Question

我遇到过这种情况，我打算插入一个生成的列，其中表达式（要设计的表达式在 (???..我也需要这个建议表达式..???) 中引用 table 下面。输出是一个计算，取决于 broker_id 的值和生成的列名 brokage 的位置。

非常感谢您对场景的分享和指导。

谢谢您，并致以诚挚的问候

新的 sqlite 学习者。

sqlite> .schema buy
CREATE TABLE buy( 
  buy_id INTEGER, 
  stock_id INTEGER, 
  investor_id INTEGER, 
  broker_id INTEGER, 
  unit INTEGER, 
  price REAL, 
  date TEXT, 
  cost REAL GENERATED ALWAYS AS (unit*price), 
  brokage REAL GENERATED ALWAYS AS (??? depend on broker_id for expression ???),
  PRIMARY KEY (buy_id, stock_id, investor_id, broker_id), 
  FOREIGN KEY (stock_id) REFERENCES stock(stock_id) ON DELETE CASCADE ON UPDATE NO ACTION, 
  FOREIGN KEY (investor_id) REFERENCES stock(investor_id) ON DELETE CASCADE ON UPDATE NO ACTION 
  FOREIGN KEY (broker_id) REFERENCES stock(broker_id) ON DELETE CASCADE ON UPDATE NO ACTION
);



sqlite> .mode column
sqlite> .header on
sqlite> SELECT * FROM buy;
buy_id  stock_id  investor_id  broker_id  unit   price  date        cost    brokage
------  --------  -----------  ---------  -----  -----  ----------  ------  --------
1       7         1            1          2000   0.68   2020-06-24  1360.0
2       25        1            3          2000   0.88   2020-10-22  1760.0

Answer 1

您可以使用 CASE 表达式来完成：

CREATE TABLE buy( 
  buy_id INTEGER, 
  stock_id INTEGER, 
  investor_id INTEGER, 
  broker_id INTEGER, 
  unit INTEGER, 
  price REAL, 
  date TEXT, 
  cost REAL GENERATED ALWAYS AS (unit*price), 
  brokage REAL GENERATED ALWAYS AS (CASE broker_id WHEN 1 THEN 9 WHEN 3 THEN 28 END),
  PRIMARY KEY (buy_id, stock_id, investor_id, broker_id), 
  FOREIGN KEY (stock_id) REFERENCES stock(stock_id) ON DELETE CASCADE ON UPDATE NO ACTION, 
  FOREIGN KEY (investor_id) REFERENCES stock(investor_id) ON DELETE CASCADE ON UPDATE NO ACTION 
  FOREIGN KEY (broker_id) REFERENCES stock(broker_id) ON DELETE CASCADE ON UPDATE NO ACTION
);

sqlite 生成的列依赖表达式

sqlite generated column dependent expression

sqlite

generated-columns