getCatalogKey：用于将选择条件转换为一组唯一键。

GetCatalogKey : Used to convert the selection criteria to a set of unique keys.

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对于主键和惟一键，只列出“非null”列并且可以选择它们定义这些键。

For primary and unique keys, only the "not null" columns are listed and can be selected to define these keys. To ease the process of defining foreign keys, the following are provided.

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产品优势：液晶同步显示歌词，红外线全遥控操作，数字选取，频段选择一键完成；前端可自由折叠，适合不同车内环境。

Advantages: LCD display synchronized lyrics, all infrared remote operation, digital selection, select a button to complete the band; front-end is free to fold, for different vehicle environments.

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