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  /*
  0.SQL
  	a.DDL
  		i.CREATE
  		ii.ALTER
  		iii.DROP
  	b.DML
  		i.SELECT
  		ii.INSERT
  		iii.UPDATE
  		iv.DELETE
  		v.TRUNCATE
  		vi.MERGE
  	c.DCL
  		i.GRANT
  		ii.REVOKE
      d.Relational Model
  		i.Set Theory
  		ii.Predicate Logic
  		iii.Missing values
  		iv.Constraint
  			a.entity 
  			b.referential 
  		v.Normalization
  			a.1NF
  			b.2NF
  			c.3NF
  		vi.Types of database systems
  			a.OLTP
  			b.DSA
  			C.DWs
  		vii.Database
  			a.System Database
  			b.User Database
  				i. Primary Filegroup .mdf
  				ii. User Filegroups .ndf
  				iii. Memory Optimized Filegroup 
  				iv. Log File .ldf
  		viii.Schemas and Objects
  
  1.Creating Tables and Defining Data Integrity
  	a.CREATE/ALTER/DROP/RENAME
  
  2.SELECT Statement
  	a.FROM
  	b.WHERE
  	c.GROUP BY
  	d.HAVING
  	e.SELECT
  		i.Expressions
  		ii.Functions
  		iii.TOP
  		iv.DISTINCT
  	f.ORDER BY
  	g.TOP
  	h.OFFSET-FETCH
  
  	Predicates and Operators
  	LIKE Predicate
  	CASE Expressions
  
  3.JOIN
  	a.CROSS JOIN
  	b.INNER JOIN
  	c.OUTER JOIN
  		i.LEFT OUTER JOIN
  		ii.RIGHT OUTER JOIN
  	d.SELF JOIN
  	e.NON-EQUI JOINS
  	f.COMPOSITE JOINS
  	g.Multi-JOIN
  
  4.Sub-Query
  	a.IN
  	b.NOT IN
  	c.EXITS
  	d.NOT EXISTS
  
  	a.Self Contained
  		i.Scalar
  		ii.Multivalue
  	b.Correlated
  		i.Scalar
  		ii.Multivalue
  
  	a.Returning previous or next values
  	b.Returning running aggregates
  
  5.Table Expressions
  	a.Derived Table
  	b.CTEs
  	c.Views
  	d.Inline Table-valued Functions
  
  6.APPLY
  	a. CROSS APPLY
  	b. OUTER APPLY
  
  7.SET
  	a.UNION (DISTINCT)
  	b.UNION ALL
  	c.INTERSECT
  	d.EXCEPT
  
  8.Window Functions
  	a.RANKING
  		i.ROW_NUMBER()
  		ii.RANK
  		iii.DENSE_RANK
  		iv.NTILE
  	b.AGGREGATE
  		i.SUM
  		ii.MIN
  		iii.MAX
  		iv.COUNT
  		v.AVG
  	c.ANALYTICAL
  		i.FIRST_VALUE & LAST_VALUE
  		ii.LAG & LEAD
  		iii.CUME_DIST
  		iv.PERCENTILE_CONT
  		v.PERCENTILE_DISC
  		vi.PERCENT_RANK
  
  9.GROUPING SETS
  	a.GROUPING SETS
  	b.CUBE
  	c.ROLLUP
  	d.GROUPING
  	e.GROUPING_ID
  
  10.PIVOT UNPIVOT
  
  11.System Functions
  	Date and Time
  		GETDATE, CURRENT_TIMESTAMP
  		DATEPART, DATENAME, DAY/MONTH/YEAR, DATEFROMPARTS, EOMONTH
  		DATEADD, DATEDIFF
  	Type Conversion
  		CAST/CONVERT, PARSE, TRY_CAST/TRY_CONVERT/TRY_PARSE, FORMAT
  	Character
  		CONCAT: CONCAT
  		Substring Extraction and position: SUBSTRING, left/right, CHARINDEX, PATINDEX
  		String length: len, DATALENGTH
  		String Alteration: replace, replicate, STUFF
  		String Formatting: lower/upper, RTRIM/LTRIM, FORMAT
  		String Splitting: STRING_SPLIT
  	CASE Expression Abbreviation: ISNULL/COALESCE,NULLIF, IIF, CHOOSE
  	Misc. object_id(), HASHBYTES, CHECKSUM
  
       
  12.INSERT
  	a.INSERT INTO
  		i.VALUES
  		ii.SELECT
  	b.INSERT EXEC
  	c.SELECT INTO	
  	d.BULK INSERT
  
  13.UPDATE
  
  14.DELETE
  
  15.TRUNCATE
  
  16.MERGE
  
  17.OUTPUT
  
  18.Conditional Logic
  	a.IF
  	b.IF ELSE
  	c.IF EXISTS
  	d.DROP [] IF EXISTS
  	e.WHILE
  	f.WHILE EXISTS
  
  19.Variables
  
  20.Temporary Tables
  	a.Local
  	b.Global
  	c.Table Variables
  	d.Table Types
  
  21.User Defined Functions
  	Scalar Function 
  	Table-valued Functions
  			a. Inline - 
  			b. Multi-Statement
  	DETERMINSTIC
  	NON-DETEMINISTIC
  
  22.Stored Procedures
  
  23.Triggers
  
  24.DYNAMIC SQL
  
  25.CURSORS
  
  26.Transaction
  	a. AutoCommit
  	b. Implicit
  	c. Explicit 
  
  27.Error
  	a. @@ERROR
  	b. TRY/CATCH
  	c. RAISERROR
  
  28.XML
  	a. XML RAW
  	b. XML AUTO 
  	c. XML PATH
  		6. XQUERY
  		   1.QUERY
  		   2.VALUE
  
  29.JSON
  
  
  */
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