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Aiden Gong commented on FLINK-22317: ------------------------------------ I investigate mysql and postgresql.Here is some scenes when drop column. 1、Table with only one column.Won't drop column and alert 'use DROP TABLE instead'. 2、Column don't exsit. Alert column don't exsit. 3、Constraint refers to this column and other column.Remove this column from Constraint.If constraint only refers to this column ,drop column and constraint together. Accoding to investigate source code of flink, found drop constraint was completed. > Support DROP column/constraint/watermark for ALTER TABLE statement > ------------------------------------------------------------------ > > Key: FLINK-22317 > URL: https://issues.apache.org/jira/browse/FLINK-22317 > Project: Flink > Issue Type: Sub-task > Components: Table SQL / API > Reporter: Jark Wu > Assignee: Aiden Gong > Priority: Major > -- This message was sent by Atlassian Jira (v8.3.4#803005)