Inserting and Querying Data in Tables
To insert or add a row of data to a table, use the insert statement.
To insert records into a table, enter the key phrases, followed by the table name, an open parenthesis, a list of column names separated by commas, a closing parenthesis, the keyword values, and a list of values contained in parentheses. The values you input will be stored in rows and will correspond to the column names you choose. Numbers should not be encased in single quotations, but strings should be.
- Put values (first column, last column) into “table name” (first column, last column).
Use the SQL SELECT query to select all the data from a table.
- Before you can query data from a table, you must first know which table you wish to query. Following that, you may specify the table name from the FROM clause.
To choose a subset of columns in a table, use the SELECT command.
- In practice, it is unusual to obtain data from all the columns in a table. In fact, just a subset of columns is required. You must provide the columns in the SELECT clause to do this.
- The following query employs the SELECT statement to retrieve all of the last names from the worker’s table’s last name field.
Using the SQL SELECT command in conjunction with additional components
- In addition to table columns, the following components can be used in the SELECT clause:
- Numbers or Strings
- Expressions
- SQL operations
- A user-defined function
The following query, for example, uses the SELECT statement in conjunction with a basic expression.
Summary
- To query data from a table, use the SELECT command.
- After the SELECT clause to which you wish to query data, specify one or more column names.
- Enter the name of the table from which you wish to get data.
Filtering Data from Tables in MySQL
The SELECT command is the most common way to get data from a MySQL database. While the basic command enables you to define the columns to display, the table to draw from, and the output format to use, the ability to filter results gives SELECT a lot more power.
Filtering queries allow you to return only the results you want by specifying specific criteria that the entries must meet. There are several ways to filter SQL queries, and in this article, we’ll go over some of the most common filtering choices for your MySQL databases: WHERE, GROUP BY, HAVING, and LIMIT.
By becoming acquainted with these optional clauses, you may learn to create searches that target the proper data, even in large databases.
Filtering Data From Tables in MySQL WHERE and DISTINCT Clauses
The WHERE clause is one of the most versatile and often used ways to express your data needs. The WHERE clause allows you to describe the conditions that a record must fulfill in order to match the query. A record is not included in the query results if it does not fulfill all of the requirements indicated by the WHERE clause.
The WHERE clause checks boolean expressions against each candidate row of data. If the result of the expression is false, the row will be eliminated from the results and will not be returned or processed further. If the result of the expression is true, it meets the search criteria and will be processed further as a candidate row.
The fundamental syntax of the where clause is as follows:
SELECT * FROM table> WHERE condition> is true;
The condition can be anything that yields a boolean result. MySQL lacks a separate built-in boolean type and instead utilizes the TINYINT type to describe boolean values. BOOLEAN and BOOL are aliases for the TINYINT type in MySQL.
Nonzero numbers are deemed true by this implementation, whereas 0 is regarded as false. To handle the opposite scenario, the constant TRUE is an alias for 1, while FALSE is an alias for 0.
While the before includes some of the most frequent test constructions, there are many additional operators that can produce boolean values that may be utilized with a WHERE clause.
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