Practice Queries
1. How to join a table with like : in one table we have data "CANADA" and in another table we have data "abc CANADA". Now i want to apply a join using like clause.
Order of Execution
Aggegation of NULLS
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Constraints
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
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;
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