TSQLCircleLive: What will be the result of the query below? Explai...

TSQLCircleLive: What will be the result of the query below? Explai...: select case when null = null then 'True' else 'False' end as ResultSet;

What will be the result of the query below? Explain your answer?

select case when null = null then 'True' else 'False' end as ResultSet;

Different types of ANSI standard joins

INNER JOIN (SIMPLE JOIN): This returns all rows for which there is at least one match in BOTH tables. This is the default type of join if no specific JOIN type is specified.

LEFT JOIN (or LEFT OUTER JOIN): This returns all rows from the left table, and the matched rows from the right table; i.e., the results will contain all records from the left table, even if the JOIN condition doesn’t find any matching records in the right table. This means that if the ON clause doesn’t match any records in the right table, the JOIN will still return a row in the result for that record in the left table, but with NULL in each column from the right table.

RIGHT JOIN (or RIGHT OUTER JOIN): This returns all rows from the right table, and the matched rows from the left table. This is the exact opposite of a LEFT JOIN. The results will contain all records from the right table, even if the JOIN condition doesn’t find any matching records in the left table. This means that if the ON clause doesn’t match any records in the left table, the JOIN will still return a row in the result for that record in the right table, but with NULL in each column from the left table.

FULL JOIN (or FULL OUTER JOIN): This returns all rows for which there is a match in EITHER of the tables. Theoretically, a FULL JOIN associations the effect of applying both a LEFT JOIN and a RIGHT JOIN; i.e., its result set is equivalent to performing a UNION of the results of left and right outer queries.

CROSS JOIN: This returns all records where each row from the first table is combined with each row from the second table (i.e., returns the Cartesian product of the sets of rows from the joined tables). Note that a CROSS JOIN can either be specified using the CROSS JOIN syntax (“explicit join notation”) or (b) listing the tables in the FROM clause separated by commas without using a WHERE clause to supply join criteria (“implicit join notation”).

What does UNION do or what result set UNION return ? What is the difference between UNION and UNION ALL?

UNION merges the contents of two structurally-compatible tables into a single combined table. This return unique records from all the table. 

The difference between UNION and UNION ALL is that UNION will omit duplicate records whereas UNION ALL will include duplicate records.

It is important to note that the performance of UNION ALL will typically be better than UNION , since UNION requires the server to do the additional task of removal of any duplicates. So, in cases where is is certain that there will not be any duplicates, or where having duplicates is not a problem, use of UNION ALL would be recommended for performance reasons.

SPACE

USE CASE: When we are working on TSQL or some text based scripting we may need some extra space in between two string, we can add space without space function as well but it is possible we may miss to put space in between string or text. If we have to maintain fixed length of space in between string every time we can use TSQL SPACE function.

SPACE

Returns a string of repeated spaces.

SYNTAX

SPACE ( integer_expression ) 

ARGUMENTS

integer_expression
Is a positive integer that indicates the number of spaces. If integer_expression is negative, a null string is returned.

REMARKS

To include spaces in Unicode data, or to return more than 8000 character spaces, use REPLICATE instead of SPACE.

EXAMPLE:-

/*

Considering employee table has three rows;

ID	FIRSTNAME	LASTNAME
1	PRIYA	KUMARI
2	AYUSH	KUMAR
3	RICHA	SINGH

*/

SELECT FirstName +’,’+SPACE(3)+LastName from employee;

PRIYA   KUMARI

AYUSH   KUMAR

RICHA   SINGH

STUFF

Use case when we are working on TSQL or Query ,some time we came such a situation when we need to replace a set of string into another set of string, this can be anything like string, character, numeric or special character. We can handle such situation using STUFF function.

STUFF

The STUFF function inserts a string into another string. It deletes a specified length of characters in the first string at the start position and then inserts the second string into the first string at the start position.

Syntax:-

STUFF (Character Expression, Start, Length, Replace with Expression)

Arguments: This function uses the following parameters.

Character Expression: Is an expression of character data. Character Expression can be a constant, variable, or column of either character or binary data.

Start: Is an integer value that specifies the location to start deletion and insertion. If start or length is negative, a null string is returned. If start is longer than the first Character Expression, a null string is returned. Start can be of type bigint.

Length: Is an integer that specifies the number of characters to delete. If length is longer than the first Character Expression, deletion occurs up to the last character in the last Character Expression. Length can be of type bigint.

Replace With Expression: Is an expression of character data. Replace with Expression can be a constant, variable, or column of either character or binary data. This expression will replace length characters of Character Expression beginning at start.

Return Types

Returns character data if character expression is one of the supported character data types. Returns binary data if character expression is one of the supported binary data types.

Remarks

If the start position or the length is negative, or if the starting position is larger than length of the first string, a null string is returned. If the start position is 0, a null value is returned. If the length to delete is longer than the first string, it is deleted to the first character in the first string.

An error is raised if the resulting value is larger than the maximum supported by the return type.

EXAMPLE

SELECT STUFF(‘abcdefgh’, 2, 3, 'xyzwsq'); 

GO

OUTPUT

-------------------

axyzwsqbcdefgh

(1 row(s) affected)