sql optimization

  1. Richard To
    Thread

    How to Tune SQL Statement with EXISTS Subquery for SQL Server I?

    The following is an example that shows a SQL statement with an Exists subquery. The SQL retrieves records from the DEPARTMENT table that DPT_ID is...
    Thread by: Richard To, Apr 12, 2021, 0 replies, in forum: SQL Server
  2. Richard To
    Thread

    How to Tune SQL Statement with IN Operator with an Expression List for SQL Server?

    The following is an example shows a SQL statement with an IN List expression. The SQL retrieves records from EMPLOYEE table that EMP_DEPT should...
    Thread by: Richard To, Apr 7, 2021, 0 replies, in forum: SQL Server
  3. Richard To
    Thread

    How to Tune SQL Statement with DECODE Expression for Oracle?

    Here the following is an example SQL statement with a DECODE expression syntax. select * from employee where decode(emp_dept, 'AAA',...
    Thread by: Richard To, Feb 1, 2021, 0 replies, in forum: Oracle
  4. Richard To
    Thread

    How to Tune SQL with IN Subquery in Certain Environment for Oracle ?

    Here is an example SQL that retrieves data from EMPLOYEE table with employee’s ID code in EMP_SUBSIDIARY table. select * from employee a where...
    Thread by: Richard To, Jan 13, 2021, 0 replies, in forum: Oracle
  5. Richard To
    Thread

    How to Tune SQL Statement with Driving Path Control for MySQL?

    The following is an example shows a SQL statement with two potential table join paths. “Employee to Department” and “Department to Employee” are...
    Thread by: Richard To, Jan 4, 2021, 0 replies, in forum: MySQL
  6. Richard To
    Thread

    How to Tune SQL with Exists Operator in Certain Environment for Oracle?

    Here is an example SQL that retrieves data from EMPLOYEE table with “emp_id < 710000” and employee’s department code exists in DEPARTMENT table....
    Thread by: Richard To, Dec 18, 2020, 0 replies, in forum: Oracle
  7. Richard To
    Thread

    How to Tune SQL Statement with IN List Bind Variables for MySQL?

    The following is an example shows a SQL statement with a variable on the IN List operator. The SQL retrieve records from EMPLOYEE table that...
    Thread by: Richard To, Dec 10, 2020, 0 replies, in forum: MySQL
  8. Richard To
    Thread

    How to Tune SQL with SEMI JOIN by Hints INDEX_DESC Injection for Oracle?

    Semi-join is introduced in Oracle 8.0. It provides an efficient method of performing a WHERE EXISTS or WHERE IN sub-queries. A semi-join returns...
    Thread by: Richard To, Dec 6, 2020, 0 replies, in forum: Oracle
  9. Richard To
    Thread

    How to Tune SQL with LIKE '%ROGER%' SQL Statements for Oracle?

    The LIKE is a logical operator that determines if a character string matches a specified pattern. A pattern may include regular characters and...
    Thread by: Richard To, Nov 26, 2020, 0 replies, in forum: Oracle
  10. Richard To
    Thread

    How to Tune Delete SQL statement with subqueries for MySQL?

    The following is an example shows a DELETE SQL statement with subquery. The SQL delete records from emp_subsidiary that should satisfy with three...
    Thread by: Richard To, Nov 23, 2020, 0 replies, in forum: MySQL
  11. Richard To
    Thread

    How to Tune SQL Statement with Multiple OR Subqueries for Oracle?

    Here the following is SQL statement with multiple OR subqueries. SELECT * FROM employee WHERE emp_id IN (SELECT emp_id FROM emp_subsidiary where...
    Thread by: Richard To, Nov 16, 2020, 0 replies, in forum: Oracle
  12. Richard To
    Thread

    How to Tune SQL with “Group By” statement?

    The following is an example shows a SQL statement with “Group by” expression. The SQL retrieve the sum of historical salary from table...
    Thread by: Richard To, Nov 10, 2020, 0 replies, in forum: MySQL
  13. Richard To
    Thread

    How to Tune SQL Statement with CASE Express for Oracle?

    Here the following is a simple SQL statement with a CASE expression syntax. SELECT * FROM employee WHERE CASE WHEN emp_salary< 1000 THEN 'low'...
    Thread by: Richard To, Nov 2, 2020, 0 replies, in forum: Oracle
  14. Richard To
    Thread

    How to Tune SQL Statement with “< All (subquery)” Operator for Oracle?

    Here the following is a simple SQL statement with a “< ALL (Subquery)” syntax. SELECT * FROM employee a WHERE a.emp_salary <ALL(SELECT...
    Thread by: Richard To, Oct 26, 2020, 0 replies, in forum: Oracle
  15. Richard To
    Thread

    How to Tune SQL Statement with multiple MAX() functions for Oracle?

    Here the following is a very simple SQL statement with two Max() functions in select list. select max(emp_salary),max(emp_id) from employee;...
    Thread by: Richard To, Oct 17, 2020, 0 replies, in forum: Oracle
  16. Richard To
    Thread

    How to Tune “Not Exists” SQL statement?

    The following is an example shows a SQL statement with “Not Exists” expression. The SQL retrieve records from emp_subsidiary that satisfy with the...
    Thread by: Richard To, Sep 29, 2020, 0 replies, in forum: MySQL
  17. Richard To
    Thread

    How to Tune SQL with OR statements?

    It is common that the performance is not good if a SQL statement with OR conditions. Let’s have an example show you how to tune those SQL...
    Thread by: Richard To, Sep 14, 2020, 0 replies, in forum: MySQL
  18. Sagar Jaybhay
    Thread

    Index In SQL Server Part 1

    Index is used to find data from the table quickly. An index is created on views and tables. It is similar to the book index. If you apply index it...
    Thread by: Sagar Jaybhay, Feb 11, 2020, 0 replies, in forum: Database
  19. Richard To
    Thread

    Speed up Aggregation Functions by Multiple Subqueries

    A SQL statement with multiple aggregation functions like the following and the emps_salary and emps_id are indexed. If you find the SQL is slow...
    Thread by: Richard To, Jun 6, 2019, 1 replies, in forum: Oracle
  20. Richard To
    Thread

    Introduce a new machine tuning tool for SQL statements

    What is machine tuning for SQL statements? Tosska SQL Tuning Expert is a SQL tuning tool that optimizes your SQL statements without the need of...
    Thread by: Richard To, Dec 11, 2017, 1 replies, in forum: Oracle
Showing results 1 to 20 of 20
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