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Difference between Delete and Truncate in oracle sql.

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 " Most important question asked in an interview" Introduction: Delete and Truncate is used to remove the data from the relational table. SQL developer have to decide where to use these both concepts. By understanding the concept, it is useful for handling the data. Well analysis of all the rows to be deleted before using truncate command. Difference: Delete Truncate It is a Data Manipulation Language command. It is a Data Definition Language command. Syntax: Delete from tablename where condition; Delete from tablename; Syntax: Truncate table tablename; Delete command is slower than truncate. Truncate command is faster. Delete contain the where clause. Truncate don’t contain the where clause. It is used to remove or delete the specified row or tuple from the table using where clause. In absence of where clause, it is used to dele...
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What is hash join in oracle with example?SQL PLSQL

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  INTRODUCTION: It is the join strategy where the one table data is loaded into the hash table for an efficient lookup. Other table data is scanned to match with the hash table which is suitable for the large datasets. Database optimizer uses the two of the smaller tables to build the hash table into the memory. Its function is used to map join key values to the hash table locations. Larger table is also scanned for each row. It's fast and efficient for quick matching of rows which is based on the join condition. It is an effective when one or both of the tables are large and cannot fit in the memory. It is also effective when the join condition is an equally predicate i.e. table1.column=table2.column. It's cost is limited to the single read pass which is over the two data sets. It is situated in the PGA and the rows are accessed without latching. It will reduce I/O by preventing the necessity of repeatedly latching and reading blocks in the database buffer cache. If the data s...
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Difference between full join and cross join-oracle sql plsql

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 Difference between full join and cross join in sql:- They behave differently to combine the rows from the two tables. FULL OUTER JOIN: It is also called as the full join .It will return all the rows when there is either match in the left table or right table. If there is no match, it will return NULL for the rows of the columns which is lacking the matching rows. Syntax: select c.*,d.*  from tableC c FULL OUTER JOIN tableD d on c.id=d.id; select e.ename,d.dname from emp e FULL OUTER JOIN dept d ON e.deptno=d.deptno; When you want to retain the unmatched rows i.e operations which is not present in the emp table and having deptno as 40.So,ename is appeared as NULL. CROSS JOIN: It returns the cartesian product of both the tables i.e. Every row of the table A is combined with every row of the table B.ON condition is not used due to not match rows. Syntax: select c.*.d.* from tableC c CROSS JOIN tableD d; select e.ename,d.dname from emp e CROSS JOIN dept d; ENAME ...
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