003 query

Queries That Select Records (Chapter – 7) Query Basics • A Microsoft Access query is a question about the information stored in Access tables • Your query can be a simple question about data in a single table, or it can be a more complex question about information stored in several tables • After run query, Microsoft Access returns only the information you requested Creating Queries in Design View • The best starting point for query creation is the Design view – – Choose Select Create  Queries  Query Design the table that has the data you want, and then click Add  Click Close Creating Queries in Design View – – – Select the fields you want to include in query Arrange the fields from left to right in the order to appear in the query results If you want to hide one or more columns, then clear the Show checkbox columns for those Creating Queries in Design View – – Choose – Choose a sort order Set your filtering criteria by place the expression into the Criteria box for the appropriate field Query Tools Design  Results  Run Save the query Getting the top records • Use the Top Values box on the Design View toolbar to see the top records produced by the query – – – – – Open query in Design view Sort table so that the records you’re most interested in are at In the Query Tools  Design Query Setup  In return box,  choose a different option the top Creating Queries by Wizard • • Create a simple Query by using wizard The Query wizard works by asking you a series of questions – Choose Create  Queries  Query Wizard Creating Queries by Wizard – Choose a query type The Query wizard includes a few common kinds of queries • • • • – – Simple Query Wizard Crosstab Query Wizard Find Duplicates Query Wizard Find Unmatched Query Wizard OK In the Tables/Queries box, choose the table that has the data you want Creating Queries by Wizard – – Add the fields you want to see in the query results Click Next Enter query name  Click Finish Understanding the SQL View • • • Behind the scenes, every query is actually a text command written in a specialized language called SQL (Structured Query Language) To take a look at the SQL command for a query, right-click the tab title, and then choose SQL view Example: SELECT Products.ID, Products.ProductName, Products.Price FROM Products WHERE (((Products.Price)>50)) ORDER BY Products.Price; Summarizing Data • Create a totals query: – – Create a new query by choosing Create➝ Queries ➝ Query Design Add the tables you want to use from the Show Table dialog box, and then click Close – – Add the fields you want to use Choose Query Tools Design  Show/Hide Totals Summarizing Data • For each field, choose an option from the Total box This option determines whether the field is used in a calculation or used for grouping • Every field must belong to one of these categories: – – – It’s used in a summary calculation (like averaging, counting, …) It’s used for grouping It’s used for filtering Summarizing Data Choice in the Total box Description Subgroups records based on the values in this field Group By Sum Adds together the values in this field Avg Averages the values in this field Min Retains the smallest value in this field Max Retains the largest value in this field Counts the number of records (no matter which field you use) Count First Retains the first value in this field Last Retains the last value in this field Summarizing Data • Example: Calculate Total for every Order Query Parameters • Query parameters let you create flexible queries by enter one pieces of information • Every time you run the query, Access prompts you to supply the missing values These missing values are the query parameters • • Usually, query parameters are used in filter conditions When run the query, you fill in the value you want to use at that particular moment Query Parameters • To create a query that uses parameters: – – – – – Create a new query by choosing Create  Queries  Query Design From the Show Table dialog box, add the tables you want to use Choose Query Tools Design Show/Hide  Parameters The Query Parameters dialog box appears Choose a name and data type for parameter Click OK to close the Query Parameters dialog box Crosstab Queries • • A crosstab query is a powerful summary tool that examines huge amounts of data and uses it to calculate information like subtotals and averages Crosstab queries use two key ingredients: grouping and summary functions – – The grouping is used to organize the rows into small sets The summary function is used to calculate a single piece of information for each group Crosstab Queries • Creating Crosstab Queries: have two ways to create a crosstab query: – – The Crosstab Query Wizard provides an automated way to create a Crosstab query The wizard works only with one table or query Build Crosstab Query by hand Crosstab Queries • Creating a Crosstab Query with the Wizard – – – – – Display the Create tab on the Ribbon Click the Query Wizard button in the Macros & Code group on the Ribbon The New Query dialog box opens Select the Crosstab Query Wizard option and then click OK Select the table or query that contains all the fields you need for your Crosstab query, and then click Next Crosstab Queries – – – Select the field(s) whose values you want to use as row headings  click Next – Choose the field whose values grouped by the row and column headings that are selected Select the field(s) whose values you want to use as column headings  click Next If select a date field as the column headings, Choose how to group dates from the list Next Crosstab Queries – – Select a grouping method from the Functions list – Name the query and then click Finish to see the Crosstab query Choose whether to include row sums by selecting the check box on the same page as the function choices, and then click Next Crosstab Queries • Creating a Crosstab query in Design view: A simple Crosstab query has three fields: – – – One used for row headings One used for column headings The Value field, which contains the data that you want to appear in the cells of the table Tell Access how to summarize your data in the Crosstab query by choosing from these choices: Sum, Avg, Min, Max, Count, StDev, Var, First, or Last Crosstab Queries – – – – Choose Create ➝ Queries ➝ Query Design – Choose the fields use for Column labels and in the Crosstab row, choose the Column Heading Add the table or query you want to use in crosstab query Query Tools  Design Query Type  Crosstab Choose the fields use for row labels and in the Crosstab row, choose the Row Heading Crosstab Queries – Select the field containing the values that you want aggregated, in the Crosstab row, choose the Value option – Set the Total row: • • Group By option for column heading and row heading Choose summarize the data for the Value field column Crosstab Queries • Example: ...  Query Wizard Creating Queries by Wizard – Choose a query type The Query wizard includes a few common kinds of queries • • • • – – Simple Query Wizard Crosstab Query Wizard Find Duplicates Query. .. to create a crosstab query: – – The Crosstab Query Wizard provides an automated way to create a Crosstab query The wizard works only with one table or query Build Crosstab Query by hand Crosstab... field Query Tools Design  Results  Run Save the query Getting the top records • Use the Top Values box on the Design View toolbar to see the top records produced by the query – – – – – Open query