{"Entry":{"collection":"sql","key":"drop-conversion","name":"DROP CONVERSION","aliases":["dropconversion"],"metadata":{"aliases":["dropconversion"],"changed_in":["7.4","8.2"],"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","compatibility","see_also"],"removed":["notes"]},"status":"changed","synopsis":{"added":["DROP CONVERSION name [ CASCADE | RESTRICT ]"],"removed":["DROP CONVERSION conversion_name"]},"to":"7.4"},{"from":"8.1","purpose_changed":false,"renamed":null,"sections":{"added":[],"changed":["parameters"],"removed":[]},"status":"changed","synopsis":{"added":["DROP CONVERSION [ IF EXISTS ] name [ CASCADE | RESTRICT ]"],"removed":[]},"to":"8.2"},{"from":"8.2","purpose_changed":false,"renamed":null,"sections":{"added":[],"changed":["parameters"],"removed":[]},"status":"changed","synopsis":null,"to":"8.3"},{"from":"8.4","purpose_changed":false,"renamed":null,"sections":{"added":[],"changed":["compatibility"],"removed":[]},"status":"changed","synopsis":null,"to":"9.0"}],"content_hash":"6eee435bd7e53be5b97157d7993d55d109f4f497336cabc206bcf1d737ebda3d","editorial":{},"first_version":"7.3","group":"type","imported_at":"2026-09-30T17:43:37.436912+08:00","last_version":"20","name":"DROP CONVERSION","object":"CONVERSION","position":3007,"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 conversion","purpose_zh":"","related":["alter-conversion","create-conversion"],"slug":"drop-conversion","source_rev":"a709ab85","synopsis":"DROP CONVERSION [ IF EXISTS ] name [ CASCADE | RESTRICT ]","verb":"DROP"}},"Definition":{"Collection":"sql","Key":"drop-conversion","SourceDatabase":"center","Version":"18","SourceTable":"sqlcmd","SourceKey":"drop-conversion","SourceRevision":"a709ab85","Facts":{"anchor":"SQL-DROPCONVERSION","file":"sql-dropconversion.html","lang":"en","name":"DROP CONVERSION","purpose":"remove a conversion","purpose_zh":"","related":["alter-conversion","create-conversion"],"sections":[{"html":"\u003cp\u003e\u003ccode class=\"command\"\u003eDROP CONVERSION\u003c/code\u003e removes a previously defined conversion. To be able to drop a conversion, you must own the conversion.\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 conversion 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\u003ename\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003eThe name of the conversion. The conversion name can be schema-qualified.\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 conversions.\u003c/p\u003e\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","key":"parameters","title":"Parameters"},{"html":"\u003cp\u003eTo drop the conversion named \u003ccode class=\"literal\"\u003emyname\u003c/code\u003e:\u003c/p\u003e\u003cpre class=\"programlisting\"\u003eDROP CONVERSION myname;\n\u003c/pre\u003e","key":"examples","title":"Examples"},{"html":"\u003cp\u003eThere is no \u003ccode class=\"command\"\u003eDROP CONVERSION\u003c/code\u003e statement in the SQL standard, but a \u003ccode class=\"command\"\u003eDROP TRANSLATION\u003c/code\u003e statement that goes along with the \u003ccode class=\"command\"\u003eCREATE TRANSLATION\u003c/code\u003e statement that is similar to the \u003ccode class=\"command\"\u003eCREATE CONVERSION\u003c/code\u003e statement in PostgreSQL.\u003c/p\u003e","key":"compatibility","title":"Compatibility"},{"html":"\u003cspan class=\"simplelist\"\u003e\u003ca href=\"/wiki/sql/alter-conversion/?v=18\" title=\"ALTER CONVERSION\"\u003e\u003cspan class=\"refentrytitle\"\u003eALTER CONVERSION\u003c/span\u003e\u003c/a\u003e, \u003ca href=\"/wiki/sql/create-conversion/?v=18\" title=\"CREATE CONVERSION\"\u003e\u003cspan class=\"refentrytitle\"\u003eCREATE CONVERSION\u003c/span\u003e\u003c/a\u003e\u003c/span\u003e","key":"see_also","title":"See Also"}],"sections_same_as":"","slug":"18","synopsis_html":"DROP CONVERSION [ IF EXISTS ] \u003cem class=\"replaceable\"\u003e\u003ccode\u003ename\u003c/code\u003e\u003c/em\u003e [ CASCADE | RESTRICT ]","synopsis_text":"DROP CONVERSION [ IF EXISTS ] name [ CASCADE | RESTRICT ]"},"ManualEvidence":{},"MeasuredEvidence":{}},"Text":{"Collection":"sql","Key":"drop-conversion","SourceDatabase":"pgweb","Version":"18","Locale":"zh-Hans","Title":"DROP CONVERSION","Summary":"移除一个转换","BodyHTML":"\u003cpre\u003eDROP CONVERSION [ IF EXISTS ] name [ CASCADE | RESTRICT ]\u003c/pre\u003e\u003csection\u003e\u003ch2\u003e描述\u003c/h2\u003e\u003cp\u003e\u003ccode\u003eDROP CONVERSION\u003c/code\u003e移除一个先前定义的转换。要能够删除一个转换，你必须拥有该转换。\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如果该转换不存在，则不要抛出错误。这种情况下会发出一个提示。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan\u003e\u003cem\u003e\u003ccode\u003ename\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e转换的名称。转换名可以是模式限定的。\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移除名为\u003ccode\u003emyname\u003c/code\u003e的转换：\u003c/p\u003e\u003cpre\u003eDROP CONVERSION myname;\n\u003c/pre\u003e\u003c/section\u003e\u003csection\u003e\u003ch2\u003e兼容性\u003c/h2\u003e\u003cp\u003eSQL 标准中没有\u003ccode\u003eDROP CONVERSION\u003c/code\u003e语句，但有一个 \u003ccode\u003eDROP TRANSLATION\u003c/code\u003e语句，它与\u003ccode\u003eCREATE TRANSLATION\u003c/code\u003e 语句配套，而后者又类似于 PostgreSQL 中的\u003ccode\u003eCREATE CONVERSION\u003c/code\u003e语句。\u003c/p\u003e\u003c/section\u003e\u003csection\u003e\u003ch2\u003e另见\u003c/h2\u003e\u003cspan\u003e\u003ca href=\"/wiki/sql/alter-conversion/?v=18\" title=\"ALTER CONVERSION\" rel=\"nofollow\"\u003e\u003cspan\u003eALTER CONVERSION\u003c/span\u003e\u003c/a\u003e, \u003ca href=\"/wiki/sql/create-conversion/?v=18\" title=\"CREATE CONVERSION\" rel=\"nofollow\"\u003e\u003cspan\u003eCREATE CONVERSION\u003c/span\u003e\u003c/a\u003e\u003c/span\u003e\u003c/section\u003e","SourceRevision":"1b5ca64c","ContentHash":"519a948cda970e15bc44cc4d4676cd8cc8b596f8fe30fe11a12f1f704609c21a","Payload":{"purpose_zh":"移除一个转换","sections":[{"html":"\u003cp\u003e\u003ccode class=\"command\"\u003eDROP CONVERSION\u003c/code\u003e移除一个先前定义的转换。要能够删除一个转换，你必须拥有该转换。\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如果该转换不存在，则不要抛出错误。这种情况下会发出一个提示。\u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003cem class=\"replaceable\"\u003e\u003ccode\u003ename\u003c/code\u003e\u003c/em\u003e\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e转换的名称。转换名可以是模式限定的。\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转换。\u003c/p\u003e\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","key":"parameters","title":"参数"},{"html":"\u003cp\u003e移除名为\u003ccode class=\"literal\"\u003emyname\u003c/code\u003e的转换：\u003c/p\u003e\u003cpre class=\"programlisting\"\u003eDROP CONVERSION myname;\n\u003c/pre\u003e","key":"examples","title":"示例"},{"html":"\u003cp\u003eSQL 标准中没有\u003ccode class=\"command\"\u003eDROP CONVERSION\u003c/code\u003e语句，但有一个 \u003ccode class=\"command\"\u003eDROP TRANSLATION\u003c/code\u003e语句，它与\u003ccode class=\"command\"\u003eCREATE TRANSLATION\u003c/code\u003e 语句配套，而后者又类似于 PostgreSQL 中的\u003ccode class=\"command\"\u003eCREATE CONVERSION\u003c/code\u003e语句。\u003c/p\u003e","key":"compatibility","title":"兼容性"},{"html":"\u003cspan class=\"simplelist\"\u003e\u003ca href=\"/wiki/sql/alter-conversion/?v=18\" title=\"ALTER CONVERSION\"\u003e\u003cspan class=\"refentrytitle\"\u003eALTER CONVERSION\u003c/span\u003e\u003c/a\u003e, \u003ca href=\"/wiki/sql/create-conversion/?v=18\" title=\"CREATE CONVERSION\"\u003e\u003cspan class=\"refentrytitle\"\u003eCREATE CONVERSION\u003c/span\u003e\u003c/a\u003e\u003c/span\u003e","key":"see_also","title":"另见"}],"sections_same_as":"","synopsis_html":"DROP CONVERSION [ IF EXISTS ] \u003cem class=\"replaceable\"\u003e\u003ccode\u003ename\u003c/code\u003e\u003c/em\u003e [ CASCADE | RESTRICT ]","synopsis_text":"DROP CONVERSION [ IF EXISTS ] name [ 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}