The other way is using the VARCHAR type, which is a special type provided by ECPG. If you use this host variable as the target variable of a query which returns a string with more than 49 characters, a buffer overflow occurs. Note that you have to take care of the length yourself. One way is using char, an array of char, which is the most common way to handle character data in C. To handle SQL character string data types, such as varchar and text, there are two possible ways to declare the host variables. Here the INTO clause appears after all the normal clauses. Here is an example using the command FETCH:ĮXEC SQL DECLARE foo CURSOR FOR SELECT a, b FROM test ĮXEC SQL FETCH NEXT FROM foo INTO :v1, :v2 The number of elements in the select list and the list after INTO (also called the target list) must be equal. So the INTO clause appears between the select list and the FROM clause. * CREATE TABLE test1 (a int, b varchar(50)) ĮXEC SQL SELECT a, b INTO :v1, :v2 FROM test SELECT is used for a query that returns only single row, and FETCH is used for a query that returns multiple rows, using a cursor. These commands have a special INTO clause that specifies which host variables the retrieved values are to be stored in. But how do you retrieve the results of a query? For that purpose, embedded SQL provides special variants of the usual commands SELECT and FETCH. Now you should be able to pass data generated by your program into an SQL command. Otherwise the preprocessor cannot handle these types since it does not know the definition. The definition of a structure or union also must be listed inside a DECLARE section. Variables that are not intended to be used in SQL commands can be declared normally outside these special sections. The declarations are also echoed to the output file as normal C variables, so there's no need to declare them again. You can have as many declare sections in a program as you like. You can also declare variables with the following syntax which implicitly creates a declare section: The variable's scope is determined by the location of its declaring section within the program. To pass data from the program to the database, for example as parameters in a query, or to pass data from the database back to the program, the C variables that are intended to contain this data need to be declared in specially marked sections, so the embedded SQL preprocessor is made aware of them.īetween those lines, there must be normal C variable declarations, such as:Īs you can see, you can optionally assign an initial value to the variable.
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