Posts Tagged ‘1Z0-001’

What is the structure of a PL/SQL block?

July 22nd, 2009

Procedural Language/Structured Query Language (PL/SQL) is a procedural language extension to SQL, the standard data access language for relational databases. PL/SQL is not an Oracle product in its own right; rather, it is a technology used by Oracle server and certain Oracle tools.

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What is DML?

July 12th, 2009

Data Manipulation Language (DML) is a category of SQL statements that query and update data in a database. Statements such as SELECT, UPDATE, INSERT, DELETE etc., are included in this category. These statements can be grouped with Data Control Language (DCL) statements.

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What is PL/SQL?

July 11th, 2009

PL/SQL is an extension of Oracle’s procedural language. It combines SQL with the structured programming language constructs, such as IF…THEN, WHILE, LOOP etc. Applications can send PL/SQL blocks to the database instead of sending individual SQL statements. This reduces network traffic.

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What is GROUP BY clause?

June 18th, 2009

The GROUP BY clause groups selected rows on the basis of values of specified column(s) for each row, and returns a single row of summary information for each group. Rows that have the same values in the specified grouping column(s) are grouped together. The GROUP BY clause suppresses duplicate rows for the grouping column(s). It does not guarantee the order of the result set. Therefore, an ORDER BY clause should be used with the GROUP BY clause to sort the result set in the desired order.

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What is HAVING clause?

June 18th, 2009

The HAVING clause sets conditions for the GROUP BY clause in a SELECT statement. It restricts the groups of rows on the basis of aggregate information. Only groups of rows, which satisfy the conditions specified in the HAVING clause are displayed. The HAVING clause cannot be used without an associated GROUP BY clause.

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What is normalization?

June 18th, 2009

Normalization is the method used to optimize databases. It is important to implement a reasonable level of normalization by creating more tables that contain fewer columns and by defining a relationship between the tables. Normalizing a logical database design involves use of formal methods to separate the data into multiple, related tables. These methods are called normalization rules.

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What is SUBSTR function?

June 17th, 2009

The SUBSTR function returns a specific portion of a character string.

Syntax:

SUBSTR (<str>, <m>[, <n>])

where,

  • str is a character string.
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    What is NVL function?

    June 17th, 2009

    The NVL function is used when a non-NULL value needs to be returned in place of a NULL value.

    Syntax:

    NVL (p1, p2)

    The NVL function takes two arguments, p1 and p2. It returns p2 if p1 is NULL. If p1 is not NULL, the function returns p1 itself.

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    What is self join?

    March 15th, 2009

    Self join joins a table to itself. Each row of the table is joined with itself and with every other row of the table.

    Example:

    SELECT F.EmployeeID, F.LastName, S.EmployeeID, S.LastName, F.Country
    FROM Employee F, Employee S
    WHERE F.Country = S.Country
    AND F.EmployeeID < S.EmployeeID
    ORDER BY F.EmployeeID, S.EmployeeID;

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    What is cardinality?

    September 10th, 2007

    Cardinality refers to the number of distinct values. For example, if a table has a cardinality of 500, it has 500 columns. Similarly, if a column has a cardinality of 20, it has 20 distinct values.

    Pass Oracle oracle-pl-sql - Oracle PL/SQL Developer Download practice question and study guide for 1Z0-001 for exam.
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