PolarDB-for-PostgreSQL

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DROP TABLE username_test;
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CREATE TABLE username_test (
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	name		text,
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	username	text not null
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);
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CREATE TRIGGER insert_usernames
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	BEFORE INSERT OR UPDATE ON username_test
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	FOR EACH ROW
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	EXECUTE PROCEDURE insert_username (username);
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INSERT INTO username_test VALUES ('nothing');
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INSERT INTO username_test VALUES ('null', null);
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INSERT INTO username_test VALUES ('empty string', '');
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INSERT INTO username_test VALUES ('space', ' ');
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INSERT INTO username_test VALUES ('tab', '	');
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INSERT INTO username_test VALUES ('name', 'name');
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SELECT * FROM username_test;
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