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Understanding Basic SQL SELECT Statements in RDBMS and ORDBMS

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This chapter focuses on the foundational aspects of SQL SELECT statements used in Relational Database Management Systems (RDBMS) and Object-Relational Database Management Systems (ORDBMS). Key objectives include differentiating between RDBMS and ORDBMS, identifying keywords and clauses, and executing various SELECT operations. Readers will learn to select all columns, specific columns, display multiple columns, use column aliases for clarity, perform arithmetic operations, remove duplicates with DISTINCT or UNIQUE, and concatenate data. Through practical examples, this chapter builds essential SQL skills for effective data retrieval.

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Understanding Basic SQL SELECT Statements in RDBMS and ORDBMS

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  1. Chapter 2Basic SQL SELECT Statements

  2. Chapter Objectives • Distinguish between an RDBMS and an ORDBMS • Identify keywords, mandatory clauses, and optional clauses in a SELECT statement • Select and view all columns of a table • Select and view one column of a table

  3. Chapter Objectives • Display multiple columns of a table • Use a column alias to clarify the contents of a particular column • Perform basic arithmetic operations in the SELECT clause

  4. Chapter Objectives • Remove duplicate lists, using either the DISTINCT or UNIQUE keyword • Combine fields, literals, and other data • Format output

  5. Relational Database Management System (RDBMS) An RDBMS is the software program used to create the database and it allows you to enter, manipulate, and retrieve data

  6. Object Relational Database Management System (ORDBMS) Same as an RDBMS except it can be used to reference objects such as maps and object fields

  7. SELECT Statement Syntax • SELECT statements are used to retrieve data from the database • Syntax gives the basic structure, or rules, for a command

  8. SELECT Statement Syntax Optional clauses and keywords are shown in brackets

  9. SELECT Statement Syntax • SELECT and FROM clauses are required • SELECT clause identifies column(s) • FROM clause identifies table(s) • Each clause begins with a keyword

  10. Selecting All Data in a Table Substitute an asterisk for the column names in a SELECT clause

  11. Selecting One Column from a Table Enter column name in SELECT clause

  12. Selecting Multiple Columns from a Table Separate column names with a comma

  13. Operations Within the SELECT Statement • Column alias can be used for column headings • Perform arithmetic operations • Suppress duplicates • Concatenate data

  14. Column Alias • List after column heading • AS keyword is optional • Enclose in double quotation marks: • If it contains blank space(s) • If it contains special symbol(s) • To retain case

  15. Column Alias Example

  16. Arithmetic Operations • Executed left to right • Multiplication and division are solved first • Addition and subtraction are solved last • Override order with parentheses

  17. Example Arithmetic Operation with Column Alias

  18. Suppressing Duplicates Enter DISTINCT or UNIQUE after SELECT keyword

  19. Concatenation • Can combine data with string literal • Use concatenation operator, || • Allows use of column alias

  20. Concatenation Example

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