为 SQLite 替换表中的数据答案

【问题标题】：Replacing Data in Table for SQLite为 SQLite 替换表中的数据
【发布时间】：2019-02-07 09:02:27
【问题描述】：

我查看了一些不同的建议，但由于某种原因，以下解决方案都无法工作/仍然在表中重复数据。

"Category" 将是此 SQLite 表的唯一值。要更改的值为“spending_limit”。

到目前为止我已经尝试过：

public void writeToSpendingLimits(int sequence, double amount){
    String sql = "INSERT OR REPLACE INTO spending_limits(category, spending_limit) "
    + "VALUES(" + sequence + ", " +  amount + ");";           
    connection.executeSQL(sql);
}

public void writeToSpendingLimits(int sequence, double amount){           
        String sql = "INSERT INTO spending_limits (category, spending_limit) "
            + "VALUES(" + sequence + ", " + amount + ") "
            + "ON CONFLICT(category)"
            + "DO UPDATE SET spending_limit = " + amount + ";";
    connection.executeSQL(sql);

public void writeToSpendingLimits(int sequence, double amount){            
    String sql = "INSERT INTO spending_limits (category, spending_limit) "
            + "VALUES (coalesce((select category from spending_limits where category = " + amount + "),"
            + "(select max(category) from spending_limits) + 1), " + amount + ");";
    connection.executeSQL(sql);

public void writeToSpendingLimits(int sequence, double amount){              
    String sql = "UPDATE spending_limits " 
            + "SET category = " + sequence + ", " + "spending_limit = " + amount + " "
            + "WHERE spending_limit = " + sequence + ";\n"
            + "INSERT INTO spending_limits(category, spending_limit) "
            + "SELECT " + sequence + ", " + amount + " "
            + "WHERE (Select Changes() = 0)";
    connection.executeSQL(sql);

【问题讨论】：

你的表架构是什么？不工作是什么意思？

标签： sql database sqlite replace

【解决方案1】：

假设您希望每个类别有一个单一的支出限制，那么您可以将该类别设为 UNIQUE 列。那么重复的类别会导致冲突，并且会执行冲突操作，例如 OR REPLACE。

例如考虑以下几点：-

DROP TABLE IF EXISTS spending_limits;
CREATE TABLE IF NOT EXISTS spending_limits (category INTEGER UNIQUE NOT NULL, spending_limit REAL);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES(1,10.23);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES(2,10.23);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES(3,10.23);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES(4,10.23);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES(5,10.23);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES('Animal',10.23);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES('Vegetable',10.23);
INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES('Mineral',10.23);
SELECT *,rowid AS rid FROM spending_limits;

INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES(1,11.23);

INSERT OR REPLACE INTO spending_limits (category, spending_limit) VALUES('Animal',11.23);

SELECT *,rowid AS rid FROM spending_limits;

这将：-

删除 spending_limits 表（如果存在）（简化测试）
创建 spending_limits 表，注意类别列具有 UNIQUE 属性。
在 spending_limits 表中插入 8 行（用于演示的混合类别类型）
选择所有行并输出
根据类别插入 2 个重复行，但数量有所调整。
- 即该语句根据类别是否已存在来插入新行或替换现有行。
选择所有行并输出它们。

结果是：-

在初始插入 8 行之后：-

在插入（替换）具有现有类别的 2 行之后：-

注意 rowid 列也会更新（因此这可能是 WITHOUT ROWID 表的候选）

【讨论】：