Có 40+ tài liệu thuộc chủ đề "giáo trình SQL"
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Unless you deliberately plan to handle this scenario, use of the implicit cursor is a declaration of faith. If the nature of the data ever changes, however, you may find that the SELECT statement which formerly. You can't get inside the separate operations of the cursor, such as the open and close stages. You can't examine the attributes of the...
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Oracle PL/SQL. This section describes the use of the %TYPE declaration attribute to anchor the datatype of one variable to another data structure, such as a PL/SQL variable or a column in a table. When you anchor a datatype, you tell PL/SQL to set the datatype of one variable from the datatype of another element.. Previously declared PL/SQL variable name....
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The second example uses a multiline comment to explain the purpose of the FOR loop. What do you think of the comments in the following Oracle Forms trigger code?. Inform the user of the problem.. None of these comments add anything to the comprehension of the code. Does the following comment explain the purpose of the code or simply restate...
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You should center all your PL/SQL development effort around packages. 1.7.4 Standardize Your PL/SQL Development Environment. This is done for you implicitly by the PL/SQL runtime engine.. Oracle PL/SQL. PL/SQL Language Fundamentals. PL/SQL Language. Introduction to PL/SQL. Next: 1.7 Best Practices for PL/SQL Excellence. PL/SQL is a powerful, many-featured product. The cursor FOR loop is one of my favorite PL/SQL...
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Previous: About the Disk Oracle PL/SQL. This disk contains the Companion Utilities Guide for Oracle PL/SQL. Oracle PL/SQL. see Section 1.4, "PL/SQL Versions". In code examples, indicates PL/SQL keywords.. Previous: Audience Oracle PL/SQL. This book was designed to be used by anyone who needs to develop Oracle-based applications using the PL/SQL programming language. particular attention to Part 4, for the...
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The function convert_date that follows illustrates the full PL/SQL version of the preceding. Oracle PL/SQL. Records in PL/SQL. The exception section of a PL/SQL block only handles exceptions raised in the execution section of that block.. An exception raised in the declaration section of a PL/SQL block is handled by the exception section of the enclosing block, if it exists.....
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10.5.3 Nonsequential Use of PL/SQL Table. The following example illustrates filling a PL/SQL table's rows randomly rather than sequentially:. "Data-Smart Row Numbers in PL/SQL Tables". 10.5.4 Passing PL/SQL Tables as Parameters. You can also pass a PL/SQL table as a parameter in a procedure or function. Declare a PL/SQL table based on the packaged type.. PL/SQL table of company IDs.....
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INSTR Returns the location in a string of the specified substring.. The following sections briefly describe each of the PL/SQL character functions.. 11.1.1 The ASCII function. The specification of the ASCII function is:. 11.1.2 The CHR function. The specification of the CHR function is:. 11.1.3 The CONCAT function. The specification of the CONCAT function is:. 11.1.4 The INITCAP function. 11.1.5...
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Get the last day of the month three months after being hired:. Tell me the number of days until the end of the month:. 12.1.3 The MONTHS_BETWEEN function. Here are some examples of the uses of MONTHS_BETWEEN:. 12.1.4 The NEW_TIME function. 12.1.5 The NEXT_DAY function. The NEXT_DAY function returns the date of the first day after the specified date which...
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RR The last two digits of the year. Q The quarter of the year, from 1 through 4. MM The number of the month in the year, from 01 through 12.. J The Julian day format of the date (counted as the number of days since January 1, 4712 B.C., the earliest date supported by the Oracle RDBMS).. MI The...
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15.3.4 Nested Blocks. A PL/SQL block nested within another PL/SQL block may be called by any of the following: nested. Each of the two SELECT-UPDATE combinations is embedded in its own anonymous PL/SQL block.. Suppose that the procedure update_management did not make use of the embedded blocks. Two of the most important concepts related to a PL/SQL block are those...
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The Benefits of Packages Overview of Package Structure The Package Specification The Package Body. That is a shame, because the package structure is also one of the most useful constructs for building well- designed PL/SQL-based applications. Oracle Corporation itself uses the package construct to extend the PL/SQL language. You can spend days and weeks, however, uncovering all the nuances and...
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Oracle PL/SQL. Functions in SQL. Previous: 17.4 Restrictions on PL/SQL Functions in SQL. Calling PL/SQL Functions in SQL. Yet it is the contents of the package body which determine whether that function is valid for execution in SQL.. You assert a purity level for a function with the RESTRICT_REFERENCES pragma, explored in the next section.. 17.5.1 The RESTRICT_REFERENCES Pragma. In...
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Does a REF sound a lot like a foreign key? While there are important differences between REFs and foreign keys (see Table 18.2), Oracle actually claims that REFs, are "more reliable and persistent". Table 18.2: Chief Differences between Foreign Keys and REFs. Restricts updates of the parent key when children exist?. Can cascade deletions of the parent to child (objects)?....
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Oracle PL/SQL. Chapter 19 Next: 19.2 Creating the New Collections. 19.1 Types of Collections. Like nested tables, they can be used in PL/SQL and in the database. Table 19.1: Storing a Nonatomic Column of Dependents in a Table of Employees Id (NUMBER) Name (VARCHAR2) Dependents_ages (Dependent_birthdate_t). with the rest of the table's data.. Table 19.2 illustrates many of the additional...
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Object Views. Object Views 19.8 Collections. Chapter 20 Next: 20.2 INSTEAD OF Triggers. Example: Using Object Views INSTEAD OF Triggers. Syntax for Object Views. Differences Between Object Views and Object Tables Not All Views with Objects Are Object Views. Object Views Housekeeping. To allow established applications to take advantage of the new object features over time, Oracle8 provides object views....
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Oracle PL/SQL. Typically, whatever is a program that interacts with the external environment: sending email, polling or controlling hardware, or invoking the C library functions that PL/SQL lacks. What we need from Oracle is a fast, reliable way of calling out to operating system commands or functions from within PL/SQL. (There is no such thing as a procedure in C.)...
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Can I say the same thing about the next version of the loop?. recommend that in order to further distinguish parameters from other PL/SQL identifiers you include the parameter mode right in the name of the formal parameter.. An OUT parameter passes a value out of the module, but its value cannot be referenced in the module. As a suffix,...
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I can now call this procedure using the default value of NET, since the Oracle Forms version of the procedure always passes a value to the stored procedure version:. (In Version 7.1 of the Oracle Server, by the way, you will be permitted to use default values in remote procedure calls.). This situation with Oracle Server Version 7 reinforces one...
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After examining the function, it was clear to me that the only way it could return a NULL was if one of the inputs was NULL. I performed a walk-through of the code and could not identify how any of the other two variables could be NULL.. After two hours of this nonsense, I finally said to myself, "Well, you...