{"Entry":{"collection":"sql","key":"drop-cast","name":"DROP CAST","aliases":["dropcast"],"metadata":{"aliases":["dropcast"],"changed_in":["8.2","9.0"],"changes":[{"from":"7.2","purpose_changed":false,"renamed":null,"sections":{"added":[],"changed":[],"removed":[]},"status":"added","synopsis":null,"to":"7.3"},{"from":"7.3","purpose_changed":true,"renamed":null,"sections":{"added":["parameters"],"changed":["description","examples","compatibility"],"removed":["notes"]},"status":"changed","synopsis":null,"to":"7.4"},{"from":"8.1","purpose_changed":false,"renamed":null,"sections":{"added":[],"changed":["parameters"],"removed":[]},"status":"changed","synopsis":{"added":["DROP CAST [ IF EXISTS ] (sourcetype AS targettype) [ CASCADE | RESTRICT ]"],"removed":[]},"to":"8.2"},{"from":"8.4","purpose_changed":false,"renamed":null,"sections":{"added":[],"changed":["parameters"],"removed":[]},"status":"changed","synopsis":{"added":["DROP CAST [ IF EXISTS ] (source_type AS target_type) [ CASCADE | RESTRICT ]"],"removed":["DROP CAST [ IF EXISTS ] (sourcetype AS targettype) [ CASCADE | RESTRICT ]"]},"to":"9.0"}],"content_hash":"921e4b33075b53e63c7e77e62ea18064f1c74d248072d0388bddb6f8c690fb59","editorial":{},"first_version":"7.3","group":"type","imported_at":"2026-09-30T17:43:37.376948+08:00","last_version":"20","name":"DROP CAST","object":"CAST","position":3001,"present_in":["7.3","7.4","8.0","8.1","8.2","8.3","8.4","9.0","9.1","9.2","9.3","9.4","9.5","9.6","10","11","12","13","14","15","16","17","18","19","20"],"purpose":"remove a cast","purpose_zh":"","related":["create-cast"],"slug":"drop-cast","source_rev":"a709ab85","synopsis":"DROP CAST [ IF EXISTS ] (source_type AS target_type) [ CASCADE | RESTRICT ]","verb":"DROP"}},"Definition":{"Collection":"sql","Key":"drop-cast","SourceDatabase":"center","Version":"18","SourceTable":"sqlcmd","SourceKey":"drop-cast","SourceRevision":"a709ab85","Facts":{"anchor":"SQL-DROPCAST","file":"sql-dropcast.html","lang":"en","name":"DROP CAST","purpose":"remove a cast","purpose_zh":"","related":["create-cast"],"sections":[{"html":"\u003cp\u003e\u003ccode class=\"command\"\u003eDROP CAST\u003c/code\u003e removes a previously defined cast.\u003c/p\u003e\u003cp\u003eTo 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.\u003c/p\u003e","key":"description","title":"Description"},{"html":"\u003cdiv class=\"variablelist\"\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eIF EXISTS\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003eDo not throw an error if the cast does not exist. A notice is issued in this case.\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003cem class=\"replaceable\"\u003e\u003ccode\u003esource_type\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003eThe name of the source data type of the cast.\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003cem class=\"replaceable\"\u003e\u003ccode\u003etarget_type\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003eThe name of the target data type of the cast.\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eCASCADE\u003c/code\u003e\u003cbr\u003e\u003c/span\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eRESTRICT\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003eThese key words do not have any effect, since there are no dependencies on casts.\u003c/p\u003e\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","key":"parameters","title":"Parameters"},{"html":"\u003cp\u003eTo drop the cast from type \u003ccode class=\"type\"\u003etext\u003c/code\u003e to type \u003ccode class=\"type\"\u003eint\u003c/code\u003e:\u003c/p\u003e\u003cpre class=\"programlisting\"\u003eDROP CAST (text AS int);\n\u003c/pre\u003e","key":"examples","title":"Examples"},{"html":"\u003cp\u003eThe \u003ccode class=\"command\"\u003eDROP CAST\u003c/code\u003e command conforms to the SQL standard.\u003c/p\u003e","key":"compatibility","title":"Compatibility"},{"html":"\u003cspan class=\"simplelist\"\u003e\u003ca href=\"/wiki/sql/create-cast/?v=18\" title=\"CREATE CAST\"\u003e\u003cspan class=\"refentrytitle\"\u003eCREATE CAST\u003c/span\u003e\u003c/a\u003e\u003c/span\u003e","key":"see_also","title":"See Also"}],"sections_same_as":"","slug":"18","synopsis_html":"DROP CAST [ IF EXISTS ] (\u003cem class=\"replaceable\"\u003e\u003ccode\u003esource_type\u003c/code\u003e\u003c/em\u003e AS \u003cem class=\"replaceable\"\u003e\u003ccode\u003etarget_type\u003c/code\u003e\u003c/em\u003e) [ CASCADE | RESTRICT ]","synopsis_text":"DROP CAST [ IF EXISTS ] (source_type AS target_type) [ CASCADE | RESTRICT ]"},"ManualEvidence":{},"MeasuredEvidence":{}},"Text":{"Collection":"sql","Key":"drop-cast","SourceDatabase":"pgweb","Version":"18","Locale":"zh-Hans","Title":"DROP CAST","Summary":"移除一个类型转换","BodyHTML":"\u003cpre\u003eDROP CAST [ IF EXISTS ] (source_type AS target_type) [ CASCADE | RESTRICT ]\u003c/pre\u003e\u003csection\u003e\u003ch2\u003e描述\u003c/h2\u003e\u003cp\u003e\u003ccode\u003eDROP CAST\u003c/code\u003e移除一个先前定义的类型转换。\u003c/p\u003e\u003cp\u003e要删除一种类型转换，你必须拥有其源数据类型或目标数据类型。这与创建该类型转换所需的权限相同。\u003c/p\u003e\u003c/section\u003e\u003csection\u003e\u003ch2\u003e参数\u003c/h2\u003e\u003cdiv\u003e\u003cdl\u003e\u003cdt\u003e\u003cspan\u003e\u003ccode\u003eIF EXISTS\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e如果该类型转换不存在，则不要抛出错误。这种情况下会发出一条提示。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan\u003e\u003cem\u003e\u003ccode\u003esource_type\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e该类型转换的源数据类型的名称。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan\u003e\u003cem\u003e\u003ccode\u003etarget_type\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e该类型转换的目标数据类型的名称。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan\u003e\u003ccode\u003eCASCADE\u003c/code\u003e\u003cbr\u003e\u003c/span\u003e\u003cspan\u003e\u003ccode\u003eRESTRICT\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e这些关键字没有任何作用，因为没有对象依赖于类型转换。\u003c/p\u003e\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e\u003c/section\u003e\u003csection\u003e\u003ch2\u003e示例\u003c/h2\u003e\u003cp\u003e要删除从类型\u003ccode\u003etext\u003c/code\u003e到类型\u003ccode\u003eint\u003c/code\u003e的类型转换：\u003c/p\u003e\u003cpre\u003eDROP CAST (text AS int);\n\u003c/pre\u003e\u003c/section\u003e\u003csection\u003e\u003ch2\u003e兼容性\u003c/h2\u003e\u003cp\u003e\u003ccode\u003eDROP CAST\u003c/code\u003e命令符合 SQL 标准。\u003c/p\u003e\u003c/section\u003e\u003csection\u003e\u003ch2\u003e另见\u003c/h2\u003e\u003cspan\u003e\u003ca href=\"/wiki/sql/create-cast/?v=18\" title=\"CREATE CAST\" rel=\"nofollow\"\u003e\u003cspan\u003eCREATE CAST\u003c/span\u003e\u003c/a\u003e\u003c/span\u003e\u003c/section\u003e","SourceRevision":"1b5ca64c","ContentHash":"7b59889444ce5822a8ecde2cc103025d7c7846b661a14dd3abc5153dd2a5ee05","Payload":{"purpose_zh":"移除一个类型转换","sections":[{"html":"\u003cp\u003e\u003ccode class=\"command\"\u003eDROP CAST\u003c/code\u003e移除一个先前定义的类型转换。\u003c/p\u003e\u003cp\u003e要删除一种类型转换，你必须拥有其源数据类型或目标数据类型。这与创建该类型转换所需的权限相同。\u003c/p\u003e","key":"description","title":"描述"},{"html":"\u003cdiv class=\"variablelist\"\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eIF EXISTS\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e如果该类型转换不存在，则不要抛出错误。这种情况下会发出一条提示。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003cem class=\"replaceable\"\u003e\u003ccode\u003esource_type\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e该类型转换的源数据类型的名称。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003cem class=\"replaceable\"\u003e\u003ccode\u003etarget_type\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e该类型转换的目标数据类型的名称。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eCASCADE\u003c/code\u003e\u003cbr\u003e\u003c/span\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eRESTRICT\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e这些关键字没有任何作用，因为没有对象依赖于类型转换。\u003c/p\u003e\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","key":"parameters","title":"参数"},{"html":"\u003cp\u003e要删除从类型\u003ccode class=\"type\"\u003etext\u003c/code\u003e到类型\u003ccode class=\"type\"\u003eint\u003c/code\u003e的类型转换：\u003c/p\u003e\u003cpre class=\"programlisting\"\u003eDROP CAST (text AS int);\n\u003c/pre\u003e","key":"examples","title":"示例"},{"html":"\u003cp\u003e\u003ccode class=\"command\"\u003eDROP CAST\u003c/code\u003e命令符合 SQL 标准。\u003c/p\u003e","key":"compatibility","title":"兼容性"},{"html":"\u003cspan class=\"simplelist\"\u003e\u003ca href=\"/wiki/sql/create-cast/?v=18\" title=\"CREATE CAST\"\u003e\u003cspan class=\"refentrytitle\"\u003eCREATE CAST\u003c/span\u003e\u003c/a\u003e\u003c/span\u003e","key":"see_also","title":"另见"}],"sections_same_as":"","synopsis_html":"DROP CAST [ IF EXISTS ] (\u003cem class=\"replaceable\"\u003e\u003ccode\u003esource_type\u003c/code\u003e\u003c/em\u003e AS \u003cem class=\"replaceable\"\u003e\u003ccode\u003etarget_type\u003c/code\u003e\u003c/em\u003e) [ CASCADE | RESTRICT ]","synopsis_text":"DROP CAST [ IF EXISTS ] (source_type AS target_type) [ CASCADE | RESTRICT ]"}},"RequestedLocale":"zh-Hans","Fallback":false,"Versions":["10","11","12","13","14","15","16","17","18","19","20","7.3","7.4","8.0","8.1","8.2","8.3","8.4","9.0","9.1","9.2","9.3","9.4","9.5","9.6"],"Locales":["en","zh-Hans"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}