How to Use and in Sql Select Statement

The next thing we want to do is not only select columns, but also select rows that we want to have in the result. To do this, we use the keyword WHERE. Let`s take a look at 3 examples: The SELECT statement is probably the most important SQL command. It is used to return the results of our databases, and no matter how simple it may seem, it could really be very complex. In this article, we will give an introduction to the SELECT declaration and cover more complex things in future articles. The SELECT statement is used to select data from a database. Let`s take a look at the syntax of the Transact-SQL SELECT statement: in the select statement, only the line with the SELECT keyword is required. After this reserved keyword, we list everything we want to see in our result. These can be values, table attributes, results of operations (mathematical or logical), etc. Let`s take a look at some simple examples: in the three SELECT statements, we used the id column in the WHERE part of the statement. Note: In a SQL SELECT statement, only the SELECT and FROM statements are required.

Other clauses such as WHERE, ORDER BY, GROUP BY, HAVING are optional. Here column1, column2,. are the field names of the table from which you want to select data. To select all the fields available in the table, use the following syntax: SELECT is usually the first word in a SQL statement. Most SQL statements are SELECT or SELECT. IN the instructions. The SQL SELECT statement is used to retrieve data from a database table that returns that data as a result table. These result tables are called result sets. All SQL commands are important and required, especially those 4 most commonly used – SELECT, INSERT, UPDATE, DELETE.

Therefore, the claim that the SELECT statement is the most important is not true. It`s just as important as others, but it`s certainly the most commonly used. Being able to write a SELECT to get exactly what you wanted is a very desirable knowledge these days. In addition to writing an instruction that returns the correct result, you almost (if you write a single query and it takes 2 seconds instead of 0.1 seconds, you can live with it) always have to make sure that the query is written optimally. Both instructions do the same thing, but for different tables. The * after SELECT means that we select all the columns in this table. The last thing we are going to do in this article is to select the data from the two tables in our model. Before we do that, let`s remember that these tables are linked by foreign keys (city.county_id = country.id). We must use this condition every time we use these two tables: the second statement returned all records with ID > 2, so our result had several rows. Note: The WHERE clause is used not only in SELECT statements, but also in UPDATE, DELETE, etc.! In today`s article, we explained the basics of the SELECT statement. In the next article, we will write more complex instructions and use other keywords such as GROUP BY, HAVING, and ORDER BY. So, stay tuned! You can also use clauses such as WHERE, GROUP BY, HAVING, ORDER BY with the SELECT statement.

We will discuss these commandments in future chapters. If a field name is contained in more than one table in the FROM clause, precede it with the table name and table name. (period) Operator. In the following example, the Department field is in both the Employees table and the Supervisors table. The SQL statement selects the services in the Employees table and the Supervisor Names table in the Supervisors table: here is a selection of the Customers table in the Northwind sample database: the most commonly used SQL command is the SELECT statement. The SQL SELECT statement is used to query or retrieve data from a table in the database. A query can retrieve information from specified columns or from all columns in the table. To create a simple SQL SELECT statement, you must specify the name of the column(s) and the name of the table. The entire query is called a SQL SELECT statement. The following SQL statement selects all clients that are in Germany, France, or the United Kingdom: this column is also the primary key of the table.

Therefore, the first selection can only find 1 record with id = 2. For the same reason, the third instruction could not find a record – there is no record with id = 6. You can also recover data from multiple columns. For example, to select the first and last names of all students. This example creates a recordset of type Dynaset based on an SQL statement that selects the LastName and FirstName fields for all records in the Employees table. It calls the EnumFields procedure that generates the contents of a Recordset object in the debug window. Use the IN OPERATOR to select all records where the country is “Norway” or “France”. You can use the other clauses in a SELECT statement to further restrict and organize the returned data. For more information, see the Help topic for the clause you are using. Note: SQL commands are not case sensitive. The above SELECT statement can also be written as follows The following SQL statement selects the CustomerName and City columns in the Customers table: To do this, the Microsoft Jet database engine searches for the specified table(s), retrieves the selected columns, selects the rows that meet the criterion, and sorts or groups the resulting rows in the specified order.

Well, I think you understand, you`re going to make the system work and analyze what`s stored in it. The analysis part is probably cooler because you`ll be able to create reports and see what happened before, and if you have enough data and statistical knowledge, you`ll be able to predict the future (as much as possible). I can hardly imagine performing analyses when working with databases without writing a SELECT statement. Specifies that all fields in the specified table(s) are selected. SELECT statements do not modify any data in the database. . You can use the IN operator to specify multiple values in a WHERE clause. As expected, we only have 2 columns in the result. While it makes sense to return only the columns that interest you, it`s even more than that later. If your table contains a large number of columns or if you join some tables, it is much more than desirable to list only the columns you need. Names to use as column headers instead of the original column names in the table.

Note: You should only list the columns that you need in the result. The probability that you will use * and return all columns is very low. You probably will only do this if you want to take a look at the contents of this table for the first time. If you use aggregated functions or queries that return ambiguous or duplicate Field object names, you must use the AS clause to provide a different name for the Field object. The following example uses the HeadCount title to name the returned Field object in the resulting Recordset object: the returned data is stored in a result table called a result set. When a Recordset object is created, the Microsoft Jet Database Engine uses the field name of the table as the Field object name in the Recordset object. If you want a different field name, or if a name is not implicit in the phrase used to generate the field, use the reserved AS word. The following example uses the title Birth to name the Field object returned in the resulting Recordset object: one of the following predicates: ALL, DISTINCT, DISTINCTROW, or TOP. You use the predicate to limit the number of records returned. If none is specified, the default value is ALL. Explains how to use expressions in the SQL SELECT statement. Regarding the use of expressions in the WHERE and ORDER BY clauses, these are explained in the respective sections.

In this series we have had 4 articles so far and we have created a simple database, filled it with some data and explained what primary and foreign keys are. These are prerequisites for “playing” with our data: if we only need a few columns from the table, we should list all the columns we need according to the SELECT keyword: in real situations, you probably won`t put all the data in the database. Data is entered manually by multiple users of your application/system or through one or more automated processes. In these cases, you will either: Name of the database that contains the tables in tableexpression if they are not in the current database. We are now ready for the next step, which is to use the data from our database. The data model is the same as the one used in the previous article. Let`s start with two simple SELECT: Some of the following examples assume that there is a hypothetical salary field in an Employees table. Note that this field does not exist in the Employees table in the Northwind database. The EnumFields subprocedure receives a Recordset object from the calling procedure. The procedure then formats and prints the recordset object fields in the debug window.

The variable is the desired print field width. Some fields may be truncated. Emil is a database professional with over 10 years of experience in everything related to databases. Over the years, he has worked in the IT and finance sectors and now works as a freelancer. His past and present engagements range from database design and coding to teaching, consulting, and writing on databases. Also not to forget, BI, create algorithms, chess, philately, 2 dogs, 2 cats, 1 woman, 1 baby. You can find it on LinkedIn See all articles from Emil Drkusic UtterAccess Community Links. UtterAccess is the main Microsoft Access help wiki and forum. NOTE: These database tables are used here for a better explanation of SQL commands. .