Introduction to SQL Structured Query LanguageWritten By The. VBProgramer. This tutorial is not directly related to Visual Basic 6. But you will use this information heavily when writing any VB6 program that accesses a database. This teaches you all the basics and then some of the SQL language it does so using Access databases. The SQL tutorial is pretty lengthy, but if you press through it you will really understand how database programming works. Prerequisites. This tutorial presumes that. Once a database has been designed and its tables have been. SQL can be used to manipulate the data in those tables. Tutorials on database. Internet sites. Even. You will need to have. MS Access 2. 00. For one of the examples, you will also need. MS Excel. About this Tutorial. The sample database used for. Download Burnout Revenge Para Pc Completo Clothing more. SQL Quick Guide Learn SQL Structured Programming Language in simple and easy steps starting from basic to advanced concepts with examples including database. What is SQL and where does it come from Structured Query Language SQL is a language that provides an interface to relational database systems. Northwind Traders. Microsoft in Visual Studio and MS Office. The original database. Microsoft NWIND. MDB contains many features that would. SQL to interact with database tables. Only rarely will you need to remove duplicate entries from a table on a production database. The tables in these databases should have a constraint, such as a primary. A table is a collection of related data held in a structured format within a database. It consists of columns, and rows. In relational databases, and flat file. Images/1482_7.jpg' alt='Sql Update Table Remove Duplicates Access' title='Sql Update Table Remove Duplicates Access' />I have 2 tables srcTable1 destTable that have identical schemas. I am trying to copy all rows from srcTable to destTable and ignore the duplicates. I thought I. I have 2 tables a main APPLICATION table that holds the core data, and a STATUSTRACKING table that reflects the status changes of the core data in the APPLICATION table. The original. database shows off many features of an MS Access database it. Cust. Name but it would appear as Customer Name. The modified version of the. NWINDVBP. MDB has stripped out all of the. Download the. NWINDVBP. MDB database here. A Note on Terminology. In this tutorial, the term record. Introduction to SQLSQL Structured Query. Language is a language designed to. Most people pronounce it sequel. I. believe either pronunciation is fine. In the mid 1. 97. SQL was. developed under the name SEQUEL for Structured English Query. Language at the IBM San Jose research facilities to be the data. IBMs prototype relational model DBMS called. System R. In 1. 98. SQL to avoid confusion. SEQUEL. SQL is currently used and. This includes. IBMs DB2, Oracle, XBase d. Base, Fox. Pro, etc., MS SQL Server, and Access. Although there are various SQL standards SQL 8. SQL 9. 2, etc. SQL spoken by. For example, there are some things you can do in Oracle. SQL that you cant do with Access, and vice versa. On its own, SQL is a. SQL. When used on its own, a SQL command is given at a. DBMS software. You can then view the. SQL command. Some DBMSs support SQL scripts also called. SQL. statements that are executed one after the other. SQL statements can also be. VB, C, COBOL, etc., where a SQL. SQL accomplishes many. SELECT, UPDATE, INSERT. DELETE, CREATE, ALTER, and DROP. Each of these seven statements fall into one. DML Data Manipulation Language statements or DDL Data. Definition Language statements. These statements are summarized as follows DML Statements. SELECT Enables you to select one or more. The results can be simply. SQL, can be processed as a temporary table called a. Access, called a cursor in other DBMSs. UPDATE Enables you to update the data in. INSERT Enables you to append rows to an. DELETE Enables you to delete one or more. DDL Statements. CREATE Enables you. ALTER Enables you to modify the structure of an. DROP Enables. The Northwind Traders Database. This tutorial uses the. Northwind Traders, a fictional company that is a distributor of. The link to download the database file, NWINDVBP. MDB, is. provided above. The Northwind Traders. Access, go. to Tools   Relationships How to do Command line SQL in Access. Open the database that you want. NWINDVBP. MDB. Select Queries from the Objects. New. The New Query dialog box. Design View pre selected as the default. Click OK. The Show Table dialog box. Click Close. The leftmost button on the Access. SQL. Click that button. A text entry box will appear. SELECT pre entered and highlighted. This is where. you type your SQL query. Try one now. Type the following. SELECT. Customer. ID, Company. Name, Contact. Name. FROM. Customers. Note SQL is NOT case sensitive. You can enter. keywords, table names, and field names in either upper or lower case letters. The only time case sensitivity is an issue is. To run the query, click the Run. Access then displays the results. To return to SQL view, select. Once you have returned to. SQL view, you can overwrite the SQL command that you entered with the next SQL. Before you overwrite the existing query, you can save. FYI To see the graphical. SQL query that you entered, select the Design. View option Whenever you write a query. SQL, Access builds the graphical representation of that query if possible. SQL queries cannot be represented. Conversely, whenever you build a query graphically, Access. SQL statement behind the scenes. Saving Queries. To save a query in the. Access database, click the Save button the diskette icon on the Access. This will enable you to recall the query from the Queries tab in. Access. If you wish to only save the. SQL statement but not save the query in Access, you can select the text you. SQL view, copy it, then paste it into another application such as. Notepad, Word, or the VB code editor. Conversely, you can type up a SQL query. Notepad or Word, copy it, then paste it into the SQL View text entry screen. When you are at the point. VB application that requires embedded SQL statements. Access to cheat. For example, if you cant recall exactly how to phrase a particular SQL. Access with the graphical designer and. If it produces the desired results, you can switch over to SQL View. Access and paste into VB. However there is no substitute for simply knowing how to get the job. DBMS that does not have a graphical. For each example in the. SQL commands as shown. The SQL. commands to key in will be shown in bold Courier, like the following SELECT. Customer. ID, Company. Name, Contact. Name. FROM. Customers. The expected results of each. Part I Single Table. Queries. The Basic SELECT Query. The SELECT query retrieves. The basic syntax is SELECT. FROM tablename. Notes If more than one. If you want to. select ALL fields from a table, you can use an asterisk instead of a list. Example 1 Retrieve all columns and all. Employees table. SELECT. FROM EMPLOPYEESExample 2 Retrieve the Product ID, product name, and unit price. Products table SELECT. Product. ID, Product. Name, Unit. Price FROM. Products. Note SQL statements can be entered on multiple. A recommended practice is to start each clause. SQL statement on a separate line. This is a style consideration only. Adding a WHERE Clause. By adding an appropriate. WHERE clause to a SELECT statement, you can limit the number of rows records. The WHERE clause specifies a condition that must be met. Note In the WHERE clause. Access will also accept double quotes, and date. Delimiting dates with the. Access most other DBMS use the single quote as the. Example 3 What is the name for product. ID 1. 9 SELECT Product. Name. FROM Products. Example 4 Which customers are from Mexico Show Customer ID. SELECT. Customer. ID, Company. Name, Contact. Name, Contact. Title. FROM. Country MexicoExample 5 Which employees were hired on October 1. Show. employee first and last name, and title in the results. SELECT First. Name, Last. Name, Title. FROM Employees. WHERE Hire. Date 1. Compound Conditions Using AND and ORExample 6 Which meatpoultry products. Category. ID 6 have less than 1. Show product ID, product. ID, and units in stock in the results. SELECT. Product. ID, Product. Name, Category. ID, Units. In. Stock. FROM. Category. ID 6 AND Units. In. Stock lt 1. Example 7 Which items in the Product. Show. product ID, product name, category ID, and units in stock in the results. SELECT. Using PLSQL Collections and Records. This chapter explains how to create and use PLSQL collection and record variables. These composite variables have internal components that you can treat as individual variables. You can pass composite variables to subprograms as a parameters. To create a collection or record variable, you first define a collection or record type, and then you declare a variable of that type. In this book, collection or record means both the type and the variables of that type, unless otherwise noted. In a collection, the internal components are always of the same data type, and are called elements. You access each element by its unique subscript. Lists and arrays are classic examples of collections. In a record, the internal components can be of different data types, and are called fields. You access each field by its name. A record variable can hold a table row, or some columns from a table row. Each record field corresponds to a table column. Collections topics Records topics Understanding PLSQL Collection Types. PLSQL has three collection types, whose characteristics are summarized in Table 5 1. Table 5 1 Characteristics of PLSQL Collection Types. Collection Type. Number of Elements. Subscript Type. Dense or Sparse. Where Created. Can Be Object Type Attribute. Associative array or index by tableUnbounded. String or integer. Either. Only in PLSQL block. No. Nested table. Unbounded. Integer. Starts dense, can become sparse. Either in PLSQL block or at schema level. Yes. Variable size array varrayBounded. Integer. Always dense. Either in PLSQL block or at schema level. Yes. Unbounded means that, theoretically, there is no limit to the number of elements in the collection. Actually, there are limits, but they are very highfor details, see Referencing Collection Elements. Dense means that the collection has no gaps between elementsevery element between the first and last element is defined and has a value which can be NULL. A collection that is created in a PLSQL block with the syntax in Collection is available only in that block. A nested table type or varray type that is created at schema level with the CREATE TYPE Statement is stored in the database, and you can manipulate it with SQL statements. A collection has only one dimension, but you can model a multidimensional collection by creating a collection whose elements are also collections. For examples, see Using Multidimensional Collections. Topics Understanding Associative Arrays Index By TablesAn associative array also called an index by table is a set of key value pairs. Each key is unique, and is used to locate the corresponding value. The key can be either an integer or a string. Using a key value pair for the first time adds that pair to the associative array. Using the same key with a different value changes the value. Example 5 1 declares an associative array that is indexed by a string, populates it, and prints it. Example 5 1 Declaring and Using an Associative Array. SQL DECLARE. 2 Associative array indexed by string. TYPE population IS TABLE OF NUMBER Associative array type. INDEX BY VARCHAR26. Associative array variable. VARCHAR26. 4. 1. Add new elements to associative array. Smallville 2. Midland 7. Megalopolis 1. Change value associated with key Smallville. Smallville 2. Print associative array. FIRST. 2. 5 WHILE i IS NOT NULL LOOP. DBMSOutput. PUTLINE. Population of i is TOCHARcitypopulationi. NEXTi. 2. 9 END LOOP. Population of Megalopolis is 1. Population of Midland is 7. Population of Smallville is 2. PLSQL procedure successfully completed. Like a database table, an associative array holds a data set of arbitrary size, and you can access its elements without knowing their positions in the array. An associative array does not need the disk space or network operations of a database table, but an associative array cannot be manipulated by SQL statements such as INSERT and DELETE. An associative array is intended for temporary data storage. To make an associative array persistent for the life of a database session, declare the associative array the type and the variable of that type in a package, and assign values to its elements in the package body. Globalization Settings Can Affect String Keys of Associative Arrays. Associative arrays that are indexed by strings can be affected by globalization settings such as NLSSORT, NLSCOMP, and NLSDATEFORMAT. As Example 5 1 shows, string keys of an associative array are not stored in creation order, but in sorted order. Sorted order is determined by the initialization parameters NLSSORT and NLSCOMP. If you change the setting of either of these parameters after populating an associated array, and then try to traverse the array, you might get an error when using a collection method such as NEXT or PRIOR. If you must change these settings during your session, set them back to their original values before performing further operations on associative arrays that are indexed by strings. When you declare an associative array that is indexed by strings, the string type in the declaration must be VARCHAR2 or one of its subtypes. However, the key values with which you populate the array can be of any data type that can be converted to VARCHAR2 by the TOCHAR function. If you use key values of data types other than VARCHAR2 and its subtypes, be sure that these key values will be consistent and unique even if the settings of initialization parameters change. For example Do not use TOCHARSYSDATE as a key value. If the NLSDATEFORMAT initialization parameter setting changes, arrayelementTOCHARSYSDATE might return a different result. Two different NVARCHAR2 values might be converted to the same VARCHAR2 value containing question marks instead of certain national characters, in which case arrayelementnationalstring. Two CHAR or VARCHAR2 values that differ only in case, accented characters, or punctuation characters might also be considered the same if the value of the NLSSORT initialization parameter ends in CI case insensitive comparisons or AI accent and case insensitive comparisons. When you pass an associative array as a parameter to a remote database using a database link, the two databases can have different globalization settings. When the remote database uses a collection method such as FIRST or NEXT, it uses its own character order, which might be different from the order where the collection originated. If character set differences mean that two keys that were unique are not unique on the remote database, the program raises a VALUEERROR exception. Understanding Nested Tables. Conceptually, a nested table is like a one dimensional array with an arbitrary number of elements. Within the database, a nested table is a column type that holds a set of values. The database stores the rows of a nested table in no particular order. When you retrieve a nested table from the database into a PLSQL variable, the rows are given consecutive subscripts starting at 1. These subscripts give you array like access to individual rows. A nested table differs from an array in these important ways An array has a declared number of elements, but a nested table does not. The size of a nested table can increase dynamically however, a maximum limit is imposedsee Referencing Collection Elements. An array is always dense that is, it always has consecutive subcripts.