Mustaqil ishlar ro’yhati

The third type is other forms of conditional sentences

Use of modal verbs in a resultative sentence
Instead of would use the verbs could be , can be , should be , etc.
For example:
If he had known , he could have helped you.
If he knew , he could help you .
You may have completed the task on time, if you had planned carefully.
You probably would have completed the assignment on time if you had planned more and more carefully.
If you were not prepared , you should have told the professor.
If you are not prepared , then you should tell the professor about it.
Use but for
Instead of if the expression can be used but for is followed by a noun. This expression is usually used in formal speech.
For example:
But if we had savings, we wouldn't be able to make the payments.
If it is not our savings, we will not be able to make payments.

10. 
    Making requests. 10. So'rovlar berish.
    

Sort data in the request
Records participating in the execution of queries can be sorted alphabetically in ascending or descending order in the Recordset dynamic data set. At the same time, it is possible to perform sorting work on the organizers of several fields (up to 10). To perform sorting, go to the column of the request form that has a field name and where sorting is required, sorting methods are shown in the Sorting line. When the mouse is clicked on this row, a list box with sorting methods will appear. Otsutstvuyet value means cancellation of sorting by this field.
Cancel the display of fields in the request
If necessary, it is possible to cancel the display of fields in the resulting set of records (even for those that are being sorted). When the indicator in the Vivod na screen row in the corresponding column of the request form is opened (turned on), the fields are reflected in the request results table. To cancel the reflection, click on the indicator (it is enough to turn it off).
Calculation in surveys
Expressions in Access
Each expression can consist of one or more operators and one or more constants, identifiers, or functions. The operator can be as complex as he likes.
Constants represent unchanging values. They are mainly used to predetermine values ​​and to compare the values ​​of table fields. The value of the constant is defined by the user when entering expressions. (for example 09, the country of the manufacturing company is Sweden).
Identifiers are the names of objects in Access (for example, table fields or queries). Identifiers are replaced by their current values ​​when evaluating expressions. (the term return value is usually used to define this action). For example, `ouse`oldInventory returns the value of the field in the current record whose field name id is defined in the expression. Named constants and variables used in Visual Basic for Applications (VBA) programs are also identifiers. There are several named internal variables that act as identifiers: True, False, Yes, No, and Null. If there are spaces in field or table names, their identifiers must be enclosed in square brackets in expressions. In order to facilitate the introduction of expressions, the table,
Functions return values ​​instead of function names in expressions. Unlike identifiers, most functions require that arguments be enclosed in parentheses, consisting of identifiers or the values ​​of partial expressions. For example, the list of arguments of the Date () function, which returns the current date, will be empty.
Operators are simple arithmetic operation symbols and other symbols or abbreviations. Most of them are equivalent to the operators of traditional programming languages ​​such as Basic. Some are unique to Access or SQL, such as Between or Like. Variables, identifiers and functions involved in operations are called operands.
There are six categories of operators for creating expressions in Access: arithmetic, assignment operators , logical operators, concatenation, function, and comparison operators.
Arithmetic operators
Arithmetic operators, as their name implies, perform addition, subtraction, multiplication and division operations. Arithmetic operators work only on numerical values ​​and have two operands except for unary and minus.
Displaying survey results
The ready request is executed after clicking the button with the image of an exclamation mark located on the Konstruktor Zaprosov toolbar. To execute a query, you can use the Open button of the database or double-click the left mouse button on the name of the selected query. Access displays on the screen the resulting set of records separated from the client table according to the specified criteria. If there is a need to make changes to the request form, then it is possible to switch to the request constructor mode using the first button from the left on the toolbar or by setting the Constructor option of the View menu.
Create other types of requests
In addition to the selective query, there are other types of queries in Access: the effective query, the parametric query and the comprehensive query.
Request for change
A change request is used to update values ​​in a table, to add or delete groups of records, and to change and move one or more tables to create a new table. There are four different types of change requests:
request to add;
deletion request;
update request;
request to create a table.
Request to add
With the help of a request to add, it is possible to add the records of one table (all or a part selected by the request) to the addition of another table. Both tables can be located in one or different databases.
If we want to add a record to another database, first of all, the source table is connected to the base where the target table is located, using the command "Syaz s tablitsami" in the "External" section of the "File" menu. In order to separate the joining records, you need to create a selection query. Then it is necessary to go to the table state using the command of the Vid menu, execute the created request and evaluate the result. After that, it returns to the constructor state and the Add command is launched from the Zapros menu. As a result, in the opened dialog window of Dobableniye, the user needs to provide the appropriate fields of the name of the table to which he wants to add the results obtained from the resulting set of query records. When we close the dialog box with the OK button, Access adds the Add line to the request form. Field names of the target table corresponding to the name of the query field are placed in this line automatically (or by the user). Then press the Start button on the toolbar to complete the request. Access will show you how many records will be added to the target table in a special dialog box, and will prompt you to confirm this action.
Removal requests
This type of request serves to delete a group of references from the table to the specified selection criteria. It is not possible to restore the records deleted using the request. Therefore, it is necessary to organize the selection criteria in a comprehensive manner. First of all, it is necessary to create a request to select the records to be deleted by specifying the criteria in the Usloviye otbora line. To check the correctness of the given criteria, this request is executed and passed to the constructor state. After that, it is necessary to start the Udaleniye command of the Zapros menu. Access adds the Udaleniye line to the request form and enters the value of Usloviye into the cell. This means that the user can set additional selection criteria. Then press the button with the exclamation mark on the toolbar and complete the request.
Update request
Using an update request, the user can change a group of records selected based on certain criteria. When creating an update request, a selection request is first created and checked. Then, in the constructor mode, the Zapros menu's Restore command is launched. As a result, Access adds a Refresh line to the request form, designed to display the new values ​​of the table fields. Computational expressions can also be used for this purpose. After pressing the Start button, Access will ask you to specify how many records of the table will be changed and change in a special dialog box.
Request to create a schedule
New tables can be created with the help of table creation request based on the result set of records of the query. Such tables are usually used to archive old records or to store backup copies of tables. It is necessary to prepare a request for the selection, and after checking the correctness of the request, a dynamic set of Recordset data is generated. If the resulting sets of records meet your requirements, return to the constructor mode and select the Zapros menu command Sozdaniye tablitsq. Access opens the Create Table dialog box to enter a name for the new table. Then the request is executed by pressing the button with the shape of an exclamation mark on the equipment panel. Access will indicate how many records will be added to the new table in a special dialog box, and will require you to confirm the execution of this action.
Indication of the results of the execution of requests
A change request changes data or copies them from one table to another. It does not create a dynamic collection of Recordsets that are displayed on the screen in table mode. To view the changes, select the change request to the selection request or create a table of the results of the request., will open to add or delete. To display the results of the execution of the update request, run the request, then display the request window to the selection in the constructor. To view updated records, set the View menu's mode tab option and switch to table mode. To display the results of adding, deleting or creating a table, select the appropriate query and press the F11 key. As a result, a database window appears on the screen. Go to the Tablist tab and double-click the name of the table to which records will be added or removed in the list of database tables.
Change request
Changing the query in the resulting set of records (for example, moving a column) is not reflected in its specification. When the request is executed again, the moved column will appear in its current position. It is recommended to change the query parameters in the constructor.
In the case of the request constructor, the following changes can be made:
giving new criteria;
change the sorting method;
cancel or set field reflection;
add, delete or change calculated expressions;
add, delete or move fields.
If the user wants to use a new or modified query in several sessions of Access, then it is necessary to save the query using the Sochranit command of the File menu. When saving a request for the first time, the Sokhraneniye object dialog box opens to give a name to the request. The request will appear in the list of requests in the database window with this name. It is recommended to save complex queries with many fields, criteria and functions. It is necessary to pay attention to this, not the results of the request , but the specification is saved. When closing requests, the Recordset dynamic set of data is lost. Therefore, it is necessary to save it separately using the Sochranit command of the File menu.

Editing requests

Editing of queries is done in constructor mode. This condition is set by clicking the Constructor button in the database window. To add a field to the request, it is copied from the list of fields at the top of the constructor window to the column of the specification field where it is necessary to put it. The field in this column and all the fields to the right of it are moved one column to the right. To delete a field, it is selected and the [Del] key is pressed or the Udalit command of the Edit menu is executed. The area that needs to be changed is determined in advance. When moving a field, the field at the pre-selected position and all the fields to the right of it will be moved to the right.