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SQL? ?? ???? ???? ??? ??? ???? ?? ???? ?? IF-ELSE ??? ????. 1. ??? ??? ?? ??? ?? ?? ?? ???? ?? ??; 2. ?? ???? ???? ?? ???? ????? ?? ??? ???? ???? ????? ?? ????. 3. ?? ??? ?? ?? ?? ??? ??? ???? ?? ??; 4. MySQL? ?? ??? ????? ?? () ??? ????? ?? SQL? ????. 5. ??? ??? If ... ?? ????? ???? ?? ??? ? ??? T-SQL? ?? ???? ??? ?????. ???, ??? ??? ??? ??? ???? ?? ??? ???? ??? ?? ????? ?? ??? ??????? NULL? ?? ?? ??? ?? ?? ???????.

Sep 07, 2025 am 12:29 AM
sql if-else
SQL ????? ?? ??? ?? ??? ??????

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???? ?? ??? ???? ?????? ???? ?? ??? ??? ???????. 1. mySQL, SqlServer ? PostgreSQL? ??? ?? ??? ???? ?? information_schema.table_constraints? ??????. 2. MySQL?? showreatetable? ???? ?? ?? ??? ???? ??? Query Information_schema ?? ?, ?? ? ? ?? ??? ????. 3. postgresql?? pg_constraint ??? ???? ???? conrelid = 'table name':: regclass? ?? ?? ?? ?? ?? ??? ???? ?? ????. 4. sqlserver?? ??? ???? conrelid = '??? ??':: regclass? ?? ?? ?? ??? ?? ? ? ??????. 4.

Sep 06, 2025 am 05:48 AM
SQL?? ??? ???? ???? ??

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Sep 06, 2025 am 05:35 AM
SQL?? ?? ?? ??? ???? ??

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Sep 06, 2025 am 05:15 AM
SQL?? ???? ? ??? ?? ??

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Sep 06, 2025 am 03:45 AM
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String_Agg? ?? ?? ?? ?? ???? ???? SQL ?? ???? ??? ??? ? ??? ??? ?????. ?? ??? string_agg (??, ?? ?)?? Orderby ?? Withing -Troup Control Order? ?? ? ? ????. ?? GroupBy ???? ?? ??, ??? ?? ?? ?? ???? ???? ? ?????. ? ??? ???? NULL ?? ???? ??, ??? ?? ??? ?? ??? ?? ???? ?????. SQLSERVER2017, PostgreSQL ?? ????? MySQL? Group_Concat? ???? Oracle? Listagg? ?????. ??? ??? ?? ??? ???? ?? ??? ??? ? ?? ? ?????? ???????.

Sep 06, 2025 am 02:34 AM
sql
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Sep 06, 2025 am 02:26 AM
SQL?? ??? ??? ???? ??

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Sep 06, 2025 am 01:03 AM
SQL?? ?? (?? ??? ?)? ?? ??? ??????

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tofindTheModeInsql, FirstGroupByTheColumnAndTeFrequencyOfeachValue.2

Sep 05, 2025 am 07:41 AM
SQL?? ?? ? ??? ?? ?? ???? ?? ??? ??????

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?? ? ??? ?? ? ?? ???? ???? ??? ?? ??? ???? ???? ?? ? ? ????. ?? ???? ??? information_schema.columns? ???? ????. 1. ?? SQL?? selectTable_namefrominformation_schema.columnswherecolumn_name = 'your_column_name'? ???? ??? ?? ?? ??? ??? ??????. ?? ??? ?? ??????? ?? ???? ?? table_schema ?? table_catalog ??? ?? ? ? ????. 2. SQLServer??? Sys.Columns ? Sys.ta? ??? ? ????

Sep 05, 2025 am 07:13 AM
sql 查找表
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ToinsertdataintoaSQLServertablewithanidentitycolumn,omittheidentitycolumnintheINSERTstatementforautomaticvaluegeneration,oruseSETIDENTITY_INSERTONtotemporarilyallowexplicitvalues,insertthedesireddataincludingtheidentityvalue,thenturnitoffwithSETIDENT

Sep 05, 2025 am 06:37 AM
SQL ?? ??? ????? ??? ??????

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Sep 05, 2025 am 06:15 AM
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Sep 05, 2025 am 04:26 AM
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Sep 05, 2025 am 01:40 AM

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