Finally, this article has presented you two ways to check the existence of data before insertion or after an update. To go further, check out this example of insert into from a SQL Server select statement.
How to create a table partition in SQL Server? So, this table have a column that stores the year of the sale and the table …. Indeed, it is obvious that splitting …. How to check the last update date on a SQL Server table? Check the last access and update with a simple SQL query? Thanks to the SQL Server relational database management system tables, ….
Follow them and you will write good code that is easy to read and to debug. The illustration below shows a completed SQL statement written the way I suggest [click the thumbnail to see a full-sized image] :.
Working with Variables. But this won't often be the case. You might be changing the criteria, fields or even data sources specified in your SQL statements each time the code is run. The information that the SQL statement needs is often obtained from the user through their choices in a dialog box or from the values in fields on a [gs form]. Forthcoming tutorials in this series will show how this can be done. You want to allow the user to choose a value for the Office criteria each time the query is run, so you build a dialog box in which there is a combo box containing a list of Offices.
The combo box is named cboOffice. You can insert a reference to the value of the combo box directly into the SQL statement:. Alternatively, you can place the value of the combo box into a variable and then insert the variable into the SQL statement:. Using a [gs variable] can make the SQL statement code easier to read and understand, especially when there are several variable criteria to consider. It is sometimes essential to use this method when the value has to be examined or manipulated in some way before it is passed to the SQL.
Whatever method you choose, you must remember to include any necessary data type qualifiers in the SQL string. In the illustration below, a single quote mark is included in the SQL string either side of the text variable marked with red arrows :.
This method requires more typing but avoids conflicts and confusion arising from nesting quotes. Remember that as with " hard-coded " criteria, variables require the correct qualifiers for their data type: quotes for text, hash-marks pound signs for dates, and nothing for numbers.
As with any other sort of programming, you SQL code can fail to work properly. It might be because you made a logic error , or got the SQL syntax wrong, or perhaps you just made a typo. If this results in workable code it might not produce the result you were expecting.
Most often though the result is code that won't run and Access throws up an error. Your job is to figure out what went wrong and put it right. Sometimes these are quite difficult to interpret.
If there is a problem Access will display an error message. It pays to familiarise yourself with the different sorts of message so that you can quickly trace the source of code errors. Most SQL errors are syntax errors.
The Jet database engine can't interpret the SQL statement because it doesn't make sense. These often arise from simple typographical errors or omissions so it is important, as with most computer programming, to take care when typing! Here are some examples NOTE : the red arrows are mine - the messages aren't that helpful!
The most common type of error is the " missing operator ". It could be a mathematical operator but it might also be a word like AND or OR , or perhaps a quote mark.
Here the quote mark before the word Brussels is missing:. Sometimes error messages are more specific and point you directly to the clause that is causing the problem. If you misspell the name of a database object such as a [gs table], or refer to one that doesn't exist, the Jet [gs database] engine will not recognise it.
These errors are usually quite easy to trace:. Not really an error message, but a response to an error in the SQL statement. Gordon Linoff Gordon Linoff 1. Yes, that would count as another problem. Everything works! You should put the comment into an answer so the OP can accept it. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science.
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