Postgresql 中文操作指南
Description
DROP CAST 删除先前定义的转换。
DROP CAST removes a previously defined cast.
要能够删除转换，你必须拥有源数据类型或目标数据类型。这些与创建转换所需的特权相同。
To be able to drop a cast, you must own the source or the target data type. These are the same privileges that are required to create a cast.
Parameters
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IF EXISTS
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Do not throw an error if the cast does not exist. A notice is issued in this case.
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source_type
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The name of the source data type of the cast.
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target_type
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The name of the target data type of the cast.
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CASCADE__RESTRICT
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These key words do not have any effect, since there are no dependencies on casts.
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Examples
要删除从类型 text 到类型 int 的转换：
To drop the cast from type text to type int:
DROP CAST (text AS int);