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https://issues.apache.org/jira/browse/IMPALA-7832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16737655#comment-16737655
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Greg Rahn commented on IMPALA-7832:
-----------------------------------
The ANSI SQL standard syntax for this would be:
{noformat}
ALTER TABLE [ IF EXISTS ] ADD [ COLUMN ] [ IF NOT EXISTS ] column_name
data_type [ COLLATE collation ] [ column_constraint [ ... ] ]
{noformat}
For example:
{noformat}
alter table t
add column if not exists c2 int,
add column if not exists c3 int;
{noformat}
> Support IF NOT EXISTS in alter table add columns
> ------------------------------------------------
>
> Key: IMPALA-7832
> URL: https://issues.apache.org/jira/browse/IMPALA-7832
> Project: IMPALA
> Issue Type: New Feature
> Components: Frontend
> Affects Versions: Impala 3.1.0
> Reporter: Thomas Tauber-Marshall
> Assignee: Fredy Wijaya
> Priority: Minor
> Labels: ramp-up
>
> alter table <table_name> add [if not exists] columns (<name> <type> [, <name>
> <type>...])
> would add the column only if a column of the same name does not already exist
> Probably worth checking out what other databases do in different situations,
> eg. if the column already exists but with a different type, if "replace" is
> used instead of "add", etc.
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