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SELECT COUNT(*) total, SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1995,1,0))"1995", SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1996,1,0))"1996", SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1997,1,0))"1997", SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1998,1,0))"1998" FROM employees; Make it sure that you will check this question again!!!! This sql statement is very similar with the previous one. select job_id as "Job..

SELECT COUNT(*) total, SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1995,1,0))"1995", SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1996,1,0))"1996", SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1997,1,0))"1997", SUM(DECODE(TO_CHAR(hire_date, 'YYYY'),1998,1,0))"1998" FROM employees; Make it sure that you will check this question again!!!! This sql statement is very similar with the previous one. select job_id as "Job..

Use WHERE clause to restrict the rows that you select.Use HAVING clause to restrict groups. SELECT department_id, AVG(salary) FROM employees WHERE AVG(salary)>8000 GROUP BY department_id; ==> This sql statement will generate an error at line 3. ==> WHERE should be HAVING

Use WHERE clause to restrict the rows that you select.Use HAVING clause to restrict groups. SELECT department_id, AVG(salary) FROM employees WHERE AVG(salary)>8000 GROUP BY department_id; ==> This sql statement will generate an error at line 3. ==> WHERE should be HAVING

NVL(expr1, expr2) Converts a null value to an actual value(expr2) NVL2(expr1,expr2,expr3) If expr1 is not null, NVL2 returns expr2. If expr1 is null, NVL2 returns expr3. The argument expr1 can have any data type. NULLIF(expr1, expr2) Compares two expressions and returns null if they are equal; returns the first expression if they are not equal. COALESCE(expr1,expr2, ... expr n) Returns the first..

NVL(expr1, expr2) Converts a null value to an actual value(expr2) NVL2(expr1,expr2,expr3) If expr1 is not null, NVL2 returns expr2. If expr1 is null, NVL2 returns expr3. The argument expr1 can have any data type. NULLIF(expr1, expr2) Compares two expressions and returns null if they are equal; returns the first expression if they are not equal. COALESCE(expr1,expr2, ... expr n) Returns the first..

TO_CHAR(date, 'format_model') The format model:Must be enclosed by single quotation marksIs case-sensitiveCan include any valid date format elementHas an fm element to remove padded blanks or suppress leading zerosIs separated from the date value by a comma

TO_CHAR(date, 'format_model') The format model:Must be enclosed by single quotation marksIs case-sensitiveCan include any valid date format elementHas an fm element to remove padded blanks or suppress leading zerosIs separated from the date value by a comma

MONTHS_BETWEEN : NUmber of months between two dates MONTHS_BETWEEN(date1,date2) The result canbe positive or negative ADD_MONTHS : Add calendar months to date ADD_MONTHS(date, n) "n" must be an integer and can be negative NEXT_DAY : Next day of the date specified NEXT_DAY(date, 'char') The value of char must be a number representing a day or a character string. LAST_DAY : Last day of the month L..

MONTHS_BETWEEN : NUmber of months between two dates MONTHS_BETWEEN(date1,date2) The result canbe positive or negative ADD_MONTHS : Add calendar months to date ADD_MONTHS(date, n) "n" must be an integer and can be negative NEXT_DAY : Next day of the date specified NEXT_DAY(date, 'char') The value of char must be a number representing a day or a character string. LAST_DAY : Last day of the month L..