SELECTPurpose. Use a SELECT statement or subquery to retrieve data from one or more tables, object tables, views, object views, or materialized views.If part or all of the result of a SELECT statement is equivalent to an existing materialized view, then Oracle Database may use the materialized view in place of one or more tables specified in the SELECT statement.This substitution is called query rewrite.It takes place only if cost optimization is enabled and the QUERYREWRITEENABLED parameter is set to TRUE.To determine whether query write has occurred, use the EXPLAINPLAN statement.Prerequisites. For you to select data from a table or materialized view, the table or materialized view must be in your own schema or you must have the SELECT privilege on the table or materialized view.For you to select rows from the base tables of a view You must have the SELECT privilege on the view, and.Whoever owns the schema containing the view must have the SELECT privilege on the base tables.The SELECTANYTABLE system privilege also allows you to select data from any table or any materialized view or the base table of any view.To issue an Oracle Flashback Query using the flashbackqueryclause, you must have the SELECT privilege on the objects in the select list.In addition, either you must have FLASHBACK object privilege on the objects in the select list, or you must have FLASHBACKANYTABLE system privilege.Syntaxselect Description of the illustration select.Description of the illustration subquery.I have a simple table Structure like this Table tempData NAME MARKS.Sql Server Update From Subquery In Oracle' title='Sql Server Update From Subquery In Oracle' />Description of the illustration queryblock.Description of the illustration subqueryfactoringclause.Description of the illustration selectlist.Description of the illustration tablereference.Sql Server Update From Subquery In Oracle' title='Sql Server Update From Subquery In Oracle' />Java2s.Emailinfo at java2s.Demo Source and Support.All rights reserved.Can you please let me know how to write sql script to store a word document as blob using base64 encoding in the oracle databse.I need to. Rewrite SQL Subqueries as Outer Joins.Oracle Tips by Burleson Consulting January 29, 2004.Misc/using_ssp_2.jpg' alt='Sql Server Update From Subquery In Oracle' title='Sql Server Update From Subquery In Oracle' />Description of the illustration flashbackqueryclause.Description of the illustration querytableexpression.Description of the illustration pivotclause.Description of the illustration pivotforclause.Description of the illustration pivotinclause.Description of the illustration unpivotclause.Description of the illustration unpivotinclause.Description of the illustration sampleclause.Description of the illustration partitionextensionclause.Description of the illustration subqueryrestrictionclause.Description of the illustration tablecollectionexpression.Description of the illustration joinclause.Description of the illustration innercrossjoinclause.Description of the illustration outerjoinclause.Description of the illustration querypartitionclause.Description of the illustration outerjointype.Description of the illustration whereclause.Description of the illustration hierarchicalqueryclause.Description of the illustration groupbyclause.Description of the illustration rollupcubeclause.Description of the illustration groupingsetsclause.Description of the illustration groupingexpressionlist.Description of the illustration expressionlist.Description of the illustration modelclause.Description of the illustration cellreferenceoptions.Description of the illustration returnrowsclause.Description of the illustration referencemodel.Description of the illustration mainmodel.Description of the illustration modelcolumnclauses.Description of the illustration modelcolumn.Description of the illustration modelrulesclause.Description of the illustration modeliterateclause.Description of the illustration cellassignment.Description of the illustration singlecolumnforloop.Description of the illustration multicolumnforloop.Description of the illustration orderbyclause.Description of the illustration forupdateclause.Semanticssubqueryfactoringclause.The WITHqueryname clause lets you assign a name to a subquery block.You can then reference the subquery block multiple places in the query by specifying the query name.Oracle Database optimizes the query by treating the query name as either an inline view or as a temporary table.You can specify this clause in any top level SELECT statement and in most types of subqueries.The query name is visible to the main query and to all subsequent subqueries except the subquery that defines the query name itself.Restrictions on Subquery Factoring This clause is subject to the following restrictions You can specify only one subqueryfactoringclause in a single SQL statement.You cannot specify a queryname in its own subquery.However, any queryname defined in the subqueryfactoringclause can be used in any subsequent named query block in the subqueryfactoringclause.In a compound query with set operators, you cannot use the queryname for any of the component queries, but you can use the queryname in the FROM clause of any of the component queries.Specify a comment that passes instructions to the optimizer on choosing an execution plan for the statement.DISTINCT UNIQUE Specify DISTINCT or UNIQUE if you want the database to return only one copy of each set of duplicate rows selected.These two keywords are synonymous.Duplicate rows are those with matching values for each expression in the select list.Restrictions on DISTINCT and UNIQUE Queries These types of queries are subject to the following restrictions When you specify DISTINCT or UNIQUE, the total number of bytes in all select list expressions is limited to the size of a data block minus some overhead.This size is specified by the initialization parameter DBBLOCKSIZE.You cannot specify DISTINCT if the selectlist contains LOB columns.ALL Specify ALL if you want the database to return all rows selected, including all copies of duplicates.The default is ALL.Specify the all column wildcard asterisk to select all columns, excluding pseudocolumns, from all tables, views, or materialized views listed in the FROM clause.The columns are returned in the order indicated by the COLUMNID column of the TABCOLUMNS data dictionary view for the table, view, or materialized view.If you are selecting from a table rather than from a view or a materialized view, then columns that have been marked as UNUSED by the ALTERTABLESETUNUSED statement are not selected.The selectlist lets you specify the columns you want to retrieve from the database.For queryname, specify a name already specified in the subqueryfactoringclause.You must have specified the subqueryfactoringclause in order to specify queryname in the selectlist.If you specify queryname in the selectlist, then you also must specify queryname in the querytableexpression FROM clause.Specify the object name followed by a period and the asterisk to select all columns from the specified table, view, or materialized view.Oracle Database returns a set of columns in the order in which the columns were specified when the object was created.A query that selects rows from two or more tables, views, or materialized views is a join.You can use the schema qualifier to select from a table, view, or materialized view in a schema other than your own.If you omit schema, then the database assumes the table, view, or materialized view is in your own schema.Specify an expression representing the information you want to select.A column name in this list can be qualified with schema only if the table, view, or materialized view containing the column is qualified with schema in the FROM clause.If you specify a member method of an object type, then you must follow the method name with parentheses even if the method takes no arguments.Specify an alias for the column expression.Oracle Database will use this alias in the column heading of the result set.The AS keyword is optional.The alias effectively renames the select list item for the duration of the query.The alias can be used in the orderbyclause but not other clauses in the query.Restrictions on the Select List The select list is subject to the following restrictions If you also specify a groupbyclause in this statement, then this select list can contain only the following types of expressions Constants.Aggregate functions and the functions USER, UID, and SYSDATEExpressions identical to those in the groupbyclause.If the groupbyclause is in a subquery, then the GROUPBY columns of the subquery must match the select list of the outer query.Any columns in the select list of the subquery that are not needed by the GROUPBY operation are ignored without error.Expressions involving the preceding expressions that evaluate to the same value for all rows in a group.Different strategies for removing duplicate records in SQL Server.Problem. In data warehousing applications during ETL Extraction, Transformation and Loading.OLTP On Line Transaction Processing applications we are often encountered.To make the table data consistent and accurate.In this tip I discuss different strategies which you can take for this, along with.Solution. There are different methods for deleting duplicate de duplication records from.I am going to discuss these methods.Using correlated subquery.Using temporary table.Creating new table with distinct records and renaming it.Using Common Table Expression CTEUsing Fuzzy Group Transformation in SSISUsing MERGE Statement.Using correlated subquery.If you already have a identity column on your table, your work is half done.You can use a correlated subquery to get rid of the duplicates.First let me briefly tell you how a correlated subquery works.In a correlated. subquery, first outer query is evaluated, the result from the outer query is used.To learn more about.In the example below, for the data deletion I am joining the inner query columns.ID you can even use minimum.Then I am deleting all.ID less than what we have got from the inner query.Please note, this approach can be taken only if you have identity column on the.ALTER TABLE permission.Script 1 De duplication with correlated subquery.CREATE TABLE Employee.ID INT IDENTITY. First.Name Varchar1. Last.Name Varchar1. Address Varchar1.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Linda, Mitchel, America.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Linda, Mitchel, America.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES John, Albert, Australia.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES John, Albert, Australia. Restful Web Services Tutorial In Java Pdf Merge there. INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES John, Albert, Australia.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.SELECT FROM Employee.Selecting distinct records.SELECT FROM Employee E1.WHERE E1. ID SELECT MAXID FROM Employee E2.WHERE E2. First. Name E1.First. Name AND E1.Last. Name E2. Last.Name. AND E1. Address E2.Address. Deleting duplicates.DELETE Employee. WHERE ID lt SELECT MAXID FROM Employee E2.WHERE E2. First. Name Employee.First. Name AND E2.Last. Name Employee.Last. Name. AND E2.Address Employee.Address. SELECT FROM Employee.Using temporary table.In this approach we pull distinct records from the target table into a temporary.Script 3. Three things you need to be aware of when you are using this approach.First you need to make sure you have or set enough size for tempdb database.Second you need to make sure you perform this operation in a transaction.TRUNCATE and INSERT parts so that you are not left with an another.Third you need to have the required permissions for object creationtruncation.Script 2, creates a table and inserts some records along with some duplicate.Script 2 Creating a table with duplicate records.CREATE TABLE Employee.First. Name Varchar1.Last. Name Varchar1.Address Varchar1.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Linda, Mitchel, America.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Linda, Mitchel, America.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES John, Albert, Australia.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES John, Albert, Australia.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES John, Albert, Australia.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.INSERT INTO EmployeeFirst.Name, Last. Name, Address.VALUES Arshad, Ali, India.SELECT FROM Employee.Script 3 Using temporary table.Pull distinct records in the temporary table.SELECT DISTINCT INTO Employee.Truncate the target table.TRUNCATE TABLE Employee.Insert the distinct records from temporary table.INSERT INTO Employee SELECT FROM Employee.Drop the temporary table.IF OBJECTIDtempdb.Employee IS NOT NULL.DROP TABLE Employee.SELECT FROM Employee.Creating new table with distinct records and renaming it.In this approach we create a new table with all distinct records, drop the existing.Please note, with this approach the meta data about the target table will change.Three things you need to aware of when you are using this approach.First you need to make sure you have enough space in your database in the.INSERT INTO. SELECT FROM to hold all the distinct records especially if.Second you need to make sure you perform this operation in a transaction.DROP and RENAME part so that you are not left with an another problem.Third you need to have required permissions for object creationdrop.Script 4 New table with distinct only.Pull distinct records in a new table.SELECT DISTINCT INTO Employee.New. Drop the old target table.DROP TABLE Employee.EXEC sprename Employee.New, Employee. SELECT FROM Employee.Using Common Table Expression CTESQL Server 2.Common. Table Expression CTE which acts as a temporary result set that is defined.SELECT, INSERT, UPDATE, DELETE, or CREATE.VIEW statement. In this example I am using a CTE for de duplication.I am using the ROWNUMBER.First. Name, Last.Name, Address columns or.I am deleting all records except where the sequential.This means keeping one record from the group and deleting all other.This is one of the efficient methods to delete records.I would suggest using this if you have SQL Server 2.Script 5 Using CTE for de duplication.SELECT ROWNUMBER OVER.PARTITION BY First.Name, Last. Name, Address.Order BY First. Name DESC, Last.Name DESC, Address DESC.FROM Employee tbl.WHERE EXISTS SELECT TOP 1 1 FROM SELECT First.Name,Last. Name,Address.GROUP BY First. Name, Last.Name, Address HAVING COUNT 1 Grp.Table. WHERE Grp.Table. First. Name tbl.First. Name AND. Grp.Table. Last. Name tbl.Last. Name AND Grp.Table. Address tbl.Address. DELETE FROM CTE Where Row.Number 1. SELECT FROM Employee.A more simplified and faster example.SELECT ROWNUMBER OVER.PARTITION BY First.Name, Last. Name, Address.Order BY First. Name DESC, Last.Name DESC, Address DESC.First. Name, Last.Name, Address. FROM Employee tbl.DELETE FROM CTE Where Row.Number 1. SELECT FROM Employee.Using Fuzzy Group Transformation in SSISIf you are using SSIS to upload data to your target table, you can use a.Fuzzy Grouping Transformation before inserting records to the destination table.Here, in the image below.Refer to Script 2 above to see more about these 9 records that were used.In the Fuzzy Grouping Transformation editor, on the Columns tab you specify the.As you can see in the below.I have chosen all 3 columns in my consideration for grouping.In the Fuzzy Grouping Transformation, you might add a conditional split to direct.Here in the example you can see.I am routing all the unique rows to the destination table and ignoring the duplicate.The Fuzzy Grouping Transformation produces a few additional columns like.Using MERGE Statement.Beginning with SQL Server 2.MERGE SQL command to perform INSERTUPDATEDELETE.This new command is similar to the UPSERT fusion.UPDATE and INSERT.Oracle. It inserts rows that dont.With the introduction of the MERGE SQL.The MERGE statement basically merges data from a source result set to a target.The new SQL command combines the sequence of conditional.INSERT, UPDATE and DELETE commands in a single atomic statement, depending on the.With this you can make sure no duplicate records are being.For more information.Next Steps. Last Update 2.About the author.Arshad Ali is a SQL and BI Developer focusing on Data Warehousing projects for Microsoft.View all my tips.
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