清单2显示具有4个元素的阵列构造函数，其值分别由NULL常数、变量、文字和标量子查询提供。

Listing 2 shows an array constructor with four elements with values given by the NULL constant, a variable, a literal and a scalar sub-query, respectively.

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包含用于列印和显示文字的常数控制项字元。

Contains constant control characters for printing and displaying text.

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包含用于列印和显示文字的常数控制项字元。

Contains constant control characters for printing and displaying text.

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