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Updating deleting predicates oracle

updating deleting predicates oracle-24

(All date functions return a value of DATE data type except the MONTHS_BETWEEN Function, which returns a number. Dual table is owned by the user SYS and can be accessed by all users.Date Functions are MONTHS_BETWEEN, ADD_MONTHS, NEXT_DAY, LAST_DAY, ROUND, TRUNC. It contains one column Dummy and one row with the value X.

updating deleting predicates oracle-35updating deleting predicates oracle-74

If I just delete it, my understanding is the data will still actually be in the data file until that space is reused.This is an interesting question: When does Oracle really delete data physically ? "): CREATE TABLE test_delete_data(id NUMBER,data VARCHAR2(100)); INSERT INTO test_delete_data VALUES (1, rpad('1', 100, '1')); INSERT INTO test_delete_data VALUES (2, rpad('2', 100, '2')); INSERT INTO test_delete_data VALUES (3, rpad('3', 100, '3')); COMMIT; SELECT dbms_rowid.rowid_to_absolute_fno(rowid, user, 'TEST_DELETE_DATA') fileno, dbms_rowid.rowid_block_number(rowid) blockno FROM test_delete_data; -- replace with values from query alter system dump datafile 4 block 16573; data_block_dump,data header at 0x8b02264 =============== [...] block_row_dump: tab 0, row 0, @0x1f2d tl: 107 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [ 2] c1 02 col 1: [100] 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 tab 0, row 1, @0x1ec2 tl: 107 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [ 2] c1 03 col 1: [100] 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 tab 0, row 2, @0x1e57 tl: 107 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [ 2] c1 04 col 1: [100] 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 end_of_block_dump block_row_dump: tab 0, row 0, @0x1f2d tl: 107 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [ 2] c1 02 col 1: [100] 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 tab 0, row 1, @0x1ec2 tl: 2 fb: --HDFL-- lb: 0x2 tab 0, row 2, @0x1e57 tl: 107 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [ 2] c1 04 col 1: [100] 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 end_of_block_dump One way to force data to actually be overwritten would be to update it to a meaningless value before deleting the row.This wouldn't work with indexes since updates are translated to delete insert in a b*tree index.For ex: Select TO_DATE (‘may 24 2007’,’mon dd rr’) from dual; Q. What is a difference between “VERIFY” and “FEEDBACK” command?Describe different types of General Function used in SQL? What is difference between COUNT (*), COUNT (expression), COUNT (distinct expression)? The MERGE statement inserts or updates rows in one table, using data from another table. VERIFY Command: Use VERIFY Command to confirm the changes in the SQL statement (Old and New values). Feedback Command: Displays the number of records returned by a query. What is the use of Double Ampersand (&&) in SQL Queries? Use “&&” if you want to reuse the variable value without prompting the user each time. Cartesian Join: When a Join condition is invalid or omitted completely, the result is a Cartesian product, in which all combinations of rows are displayed.(Where expression is any column name of Table) COUNT (*): Returns number of rows in a table including duplicates rows and rows containing null values in any of the columns. A sub query is a SELECT statement that is embedded in a clause of another SELECT statement. For ex: Select empno, ename, &&column_name from employee order by &column_name; Q. To avoid a Cartesian product, always include a valid join condition in a “where” clause.

COUNT (EXP): Returns the number of non-null values in the column identified by expression. Sub query can be placed in WHERE, HAVING and FROM clause. What are Joins and how many types of Joins are there? To Join ‘N’ tables together, you need a minimum of N-1 Join conditions.

Explain character, number and date function in detail?

Character functions: accept character input and return both character and number values.

“AS” Keyword before the alias name makes the SELECT clause easier to read. Date and character literals must be enclosed within single quotation marks (‘ ‘), number literals need not. Describe in brief different types of SQL functions? SQL functions can take arguments but always return some value.

For ex: Select empname AS name from employee; (Here AS is a keyword and “name” is an alias). For ex: Select last_name||’is a’||job_id As “emp details” from employee; (Here “is a” is a literal). There are two distinct types of SQL functions: Frequently Asked SQL Interview Questions & Answers Q.

Equi Join: This type of Join involves primary and foreign key relation. Non-Equi Joins: A Non-Equi Join condition containing something other than an equality operator.