Question

我有一个包含计算VARCHAR列的表，最多包含106个字符：

CREATE TABLE report (
    report_id INT IDENTITY(1, 1) NOT NULL,
    name VARCHAR(100) COLLATE Modern_Spanish_CI_AI NOT NULL,
    city_id VARCHAR(6) COLLATE Modern_Spanish_CI_AI,

    unique_name AS
    CASE
        WHEN city_id IS NULL
        THEN name
        ELSE name + REPLICATE(' ', 100 - LEN(name)) + city_id
    END COLLATE Modern_Spanish_CI_AI,

    CONSTRAINT report_pk PRIMARY KEY (report_id)
);

/* Report name is unique per city (and among city-less rows) */
CREATE UNIQUE INDEX report_idx1 ON report (unique_name);

但是当我运行声明时，我收到了这个警告：

警告！最大密钥长度为900字节。索引'report_idx1' 最大长度为8000字节。对于一些大的组合值，插入/更新操作将失败。

有没有办法告诉SQL Server该列不会超过106个字符，所以我摆脱了警告？

Answer 1

试试CAST(CASE ... END AS VARCHAR(106)) ...

CAST(CASE
    WHEN city_id IS NULL
    THEN name
    ELSE name + REPLICATE(' ', 100 - LEN(name)) + city_id
END AS VARCHAR(106)) COLLATE Modern_Spanish_CI_AI

或者完全忽略它......这只是一个警告。

计算列的索引触发900字节索引大小限制

1 个答案: