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ORACLE-SQL

Query Questions

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- October 08, 2022

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Sequence

- January 11, 2022

Generate Unique Sequential values Sequence has 2 pseudocolumns 1. CURRVAL 2. NEXTVAL CURRVAL : gives the most recently generated value NEXTVAL : gives the next available value in the sequence to generate sequence will start generating value from its MINVALUE Default MINVALUE is 1 default incremental value of sequence is +1 Same sequence can be used in multiple tables but not suggestable. One sequence for one table.

Constraints

- March 26, 2021

Define based on business rulex. 1. Not Null : a. Doesnot allow any Null values. b. Can be define at column level only. 2. Default : a. Filled with default value if we donot provide any value b. There is no restriction for the no of default value in one table. 3. Check : a. Allows only a valid range of values b. Can be define at column level or table level. c. Can be define at one column only ( not more than one column) d. Cannot be define on composite key 4. Unique : a. Doesnot allow duplicate value b. ...

Finding rows that only have duplicate values in a specific column

- October 11, 2022

WITH cte AS ( SELECT colb, COUNT(*) AS dup FROM sales GROUP BY colb ) SELECT cola FROM data INNER JOIN cte ON data.colb = cte.colb WHERE cte.colb > 1;