Sequence In Snowflake | What is Sequence In Snowflake

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Snowflake Sequence

Snowflake में "sequence" एक database object है जो automatic numeric values generate करता है। ये values एक particular order में increment करते हैं।

Sequences commonly primary keys या unique identifiers generate करने के लिए use किये जाते हैं।

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Snowflake Sequence Syntax

CREATE [ OR REPLACE ] SEQUENCE [ IF NOT EXISTS ] <name>
  [ WITH ]
  [ START [ WITH ] [ = ] <initial_value> ]
  [ INCREMENT [ BY ] [ = ] <sequence_interval> ]
  [ { ORDER | NOORDER } ]
  [ COMMENT = '<string_literal>' ]

Snowflake Sequence Example

नीचे दिए गए example में increase_by_one नाम से जो हर बार 1 से value increase करेगा।

Copy
-- create sequence
CREATE OR REPLACE SEQUENCE increase_by_one START = 1 INCREMENT = 1;

-- show all sequences
show sequences;

increase value get करने के लिए sequence की nextval property होती है जो हर बार incremental value return करेगी।

Copy
SELECT increase_by_one.nextval;

output

+---------+
| NEXTVAL |
|---------|
|       1 |
+---------+

Run again

Copy
SELECT increase_by_one.nextval;

Output

+---------+
| NEXTVAL |
|---------|
|       2 |
+---------+

increase_by_one.nextval का use करके किसी table के auto increment field में values insert करते time use कर सकते हो।

single query में आप multiple call भी कर सकते हैं।

Copy
SELECT increase_by_one.nextval a, increase_by_one.nextval b, increase_by_one.nextval c;

output

+----+----+----+
| a  | b  | c  |
+----+----+----+
| 3  | 4  | 5  |
+----+----+----+

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Snowflake Alter Sequence

किसी existing sequence को modify करने के लिए ALTER SEQUENCE statement का use किया जाता है।

Syntax

ALTER SEQUENCE [ IF EXISTS ] <name> RENAME TO <new_name>

ALTER SEQUENCE [ IF EXISTS ] <name> [ SET ] [ INCREMENT [ BY ] [ = ] <sequence_interval> ]

ALTER SEQUENCE [ IF EXISTS ] <name> SET
  [ { ORDER | NOORDER } ]
  [ COMMENT = '<string_literal>' ]

Alter Sequence Example

Copy
ALTER SEQUENCE increase_by_one RENAME TO increaseByOne;

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Snowflake Drop Sequence

किसी existing sequence को modify करने के लिए DROP SEQUENCE statement का use किया जाता है।

Syntax

DROP SEQUENCE [ IF EXISTS ] <name> [ CASCADE | RESTRICT ]

Example

Copy
DROP SEQUENCE IF EXISTS increaseByOne;

I Hope , आपको Snowflake में SEQUENCE के बारे में अच्छे से समझ आया होगा।

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