How to use SQL in VF I just don t know how to tie it together

I don't quite understand what you mean.

These are all simple and commonly used basic SQL statements, go here to learn the version of the reference materials.

For example, if you have a student table in your database, the table contains id, name and other elements select namefrom studentwhere id='123';Query the name of the person with ID number 123.

Take a look at the help files that come with VFP.

into cursor generates a temporary table, followed by a temporary table name.

into destination

Specify where to save the query results. If both the into clause and the to clause are included in the same query, the to clause does not work. If you don't include an into clause, the query results are displayed in the Browse window.

You can also use to direct the output of query results to a printer or file.

destination can be one of the following clauses:

array arrayname to save the query results to an array of variables. If the query results do not contain any records, this array is not created.

cursor cursorname saves the query results to a temporary table. If you specify the name of an open table, Visual FoxPro produces an error message. After the SELECT statement is executed, the temporary table remains open, active, but read-only.

Once the temporary table is closed, it is automatically deleted. The temporary table exists as a temporary file on the drive specified by sortwork.

The purpose of including nofilter is to create a pointer that can be used in later queries. Previous versions of Visual FoxPro required an additional constant or expression to act as a filter to create a pointer that could be used in later queries.

select *,t. from customers into cursor myquery

Inclusion of a nofilter reduces the number of queries because temporary tables are built on disk, and when a temporary table is deleted, the pointer is closed.

dbf tablename |table tablename to save the query results to a table. If the specified table is already open, and Set Safety is set to OFF, Visual FoxPro overrides the table without warning. If no extension is specified, Visual FoxPro specifies that the extension of the table is .

After the statement is executed, the table remains open.

Include Database DatabaseName to specify the database to which the table is added. Contains namelongtablename You can name a long name that can contain up to 128 characters and can be used in the database instead of a short name.

Right-click --- in the Query Designer window

View the SQL statement and display it with a single click.

1. First, you need to create one or two basic tables to be queried. You should be.

2. Click Tools, Wizards, and Query Wizards.

3. Select the table and field you want to query. Next.

4. Select the filter conditions, generally the two table joins must have key fields. Next step or finish.

5. Select a sorting method. Next step or finish.

6. Preview whether the query is the desired result. If so, select Save to query and modify it in the query designer.

7. Click Save. Then you open the query designer.

8、ok!Click on the SQL button on the Query Designer tool window, and you will see the SQL query statement. Just copy it and stick it to the corresponding position.

Alternatively, you can open the query designer directly with the modi query command.

Why do so many people choose to take the VF.

When the vf enters the execution statement, create table xsqk is entered before the statement is finished, so an error will be reported. Write it together with the following column definitions before executing.

insert into "Table Name" (field name table) value (expression table).

For example, you need to have a record in the student registration form, and the fields are named: student number, name, gender, and ethnicity1If you add a record, each field has a value, the command is as follows:

insert into student status value("1001"，"Wang Xiaoer"，"Male"，"Han")

If you add a record, only the values of the specified fields are added. For example, only the name and nationality are available, and the other fields have no valueInsert into student registration (name, nationality) value("Wang Xiaosan"，"Full")

Use order by time desc If you want to go to the first number of records, you can add top (number of records).

Pay attention to the information.

The field type processed by the sum function must be numeric and cannot be of any other data type, such as characters or dates.

Related functions. cumsum

Related introductions. excel

A function is defined in Microsoft Excel as: A function is a pre-written formula that can perform an operation on one or more values and return one or more values. Functions can simplify and shorten formulas in a worksheet, especially when performing long or complex calculations with formulas.

In Microsoft Excel, the sum function is applied as follows.

DescriptionSum is specified as a parameter (in Microsoft Excel, a parameter is a value that provides information about an action, event, method, property, function, or procedure. ) of all the numbers.

Each parameter can be a region (in Microsoft Excel, "region" means: two or more cells on a worksheet. Cells in a region can be adjacent or not adjacent.

Cell Reference (In Microsoft Excel, "Cell Reference" refers to the set of coordinates used to represent the position of a cell on a worksheet. For example, a cell that appears at the intersection of column b and row 3 is referenced as "b3".

Arrays (Arrays in Microsoft Excel are a single formula that can produce multiple results or perform operations on a set of parameters arranged in rows and columns. Array regions share a formula; An array constant is a set of constants that are used as parameters.

Constants (In Microsoft Excel, "constants" are values that are not calculated. For example, the number 210 and the text "quarterly earnings" are constants.

Neither the expression nor the value computed from the expression is a constant. ), formula (in Microsoft Excel, a formula is a combination of a series of values, cell references, names, or operators in a cell that produces a new value.)

Formulas always start with an equal sign (=). or the result of another function. For example, sum(a1:

a5) adds all the numbers in cells A1 to A5, for example, sum(a1, a3, a5) adds the numbers in cells A1, A3, and A5.

Syntax sum(number1,[number2],.The sum function syntax has the following parameters (parameters: values that provide information about an action, event, method, property, function, or procedure.

number1 is required. The first numeric parameter you want to add.

number2,,.Optional. Between 2 and 255 numeric parameters that you want to add.

Describes how if the parameter is an array or reference, only the numbers in it are calculated. Blank cells, logical values, or text in arrays or references are ignored. Excel displays an error if any of the parameters are incorrect values or text that cannot be converted to numbers.

No, sum is a vertical sum, which is vertical, and cannot be summed horizontally.

You should use: select student number, name, Chinese + Mathematics + English as total score from grade group by student number.

sum(expression).

Only one expression is allowed in this function format, and it is a vertical sum of expressions. So your function is completely in the wrong format.

I don't know if the database you are using is an oracle.

In oracle there is a function that is nvl(a,b), which means that when a is null, it returns b, and if a is not null, it returns a, then the sql text can be written like this.

select nvl(,0) from emp t1 where ..

No, generally sum is to sum a certain field, but it can be controlled in the program.