SELECT statement

The SAS SELECT statement is great for conditional processing because it has a mandatory OTHERWISE clause built into it to help catch unforeseen conditions. In a SAS SELECT statement, the code above would look like the code in the following program. 

Here you can see that each adverse event that was experienced has now been merged with each concomitant medication taken during that time. This is due to the SQL SELECT statement ON clause, which allows for complicated logic to be applied to the join. 

Filter. A query or set of criteria designed to select a subset of a given set of data or results. Fliters are usually applied to limit the number of hits from a search, or to limit the input to some analysis. Sometimes filters are designed to remove invalid rows of data, to randomly select a subset, or to remove rows based on the values of certain fields. A common application of filtering is in reagent selection, where reactive groups, multi-functional structures, or cost criteria may be applied to the selection of compounds for reactions. A filter can usually be expressed as a SELECT statement in a database search. 

Logic in Query Features. Using AND, OR, and NOT as modifiers on the application of query features. For example, one could run a search to select structures that contain "halogen and not primary or secondary amine, or not halogen and any amine." The logic can be a part of the query substructure, as with Markush queries, or it can be part of the SELECT statement. 

Notice the use of the Where clause, similar to its use in the Select statement. It is important to use Where with Update. Otherwise every row of... 

An SQL view is very similar to a table. It has rows and columns of defined data types just as a table. A view is defined by selecting particular rows and columns from one or more tables, using an SQL select statement. For example ... 

The results of a Select statement are in the form of a table. This can be a subset of a single table, or the result of joining several tables. The exact set of rows is chosen by using various Where clauses. The use of Boolean operation such as and, or, and not allows a sort of union (or), intersection (and), and difference (not). For example ... 

When data are selected from tables that are not related to one another, a different approach is used. The SQL operators union, intersect, and exclude allow set operations on tables or the sets of rows resulting from a select statement. For example ... 

Selecting rows from a table is only one common operation needed for a client program to work with an RDBMS. In addition to a simple SQL select statement, other more complex select statements will become necessary as more complex client programs are developed. It is also important to see how to properly use the SQL Insert statement. Rather than showing examples in several computer languages, the use of more complex SQL statements is discussed in Chapter 12. 

Rather than individual program statement or lines, SQL combines clauses into one statement to produce a result. A simple select statement might look like this ... 

What might be desired instead is a test set of 8 amines and 12 acids for a total of 96 rows. This can be accomplished if the amines are selected separately from the acids, each in a select statement of their own. The following SQL will accomplish this. 

Table 6.2 shows the first few rows selected by this SQL statement. This is the result that was desired a total of 96 compounds consisting of a combination of 8 amines and 12 acids. These separate select statements are typically called subselect clauses of an SQL statement. They are enclosed in parentheses and named uniquely. They function as if they were tables themselves, but are actually subsets, or subselects of a table. There can be any number of subselects in an SQL statement and the subselect clause itself can be more complex than shown above. For example, one might also restrict the selected amines by molecular weight, vendor, or other criteria. 

As discussed in Chapter 3, a view is a subset of a table defined by a select statement. This is quite similar to the subselect statement discussed above. Such subselect statements are sometimes also called in-line views. Here we discuss the use of views as a persistent way to store subselect statements for use in SQL statements. 

Here, the md5 function is a hash function available in PostgreSQL. It is used as a method to partition the logp values in the properties table into two arbitrary sets of about the same size. The less than operator ensures exactly two sets, and the use of the md5 function ensures that the sets are arbitrary and of about the same size. Note that using md5 results in arbitrary but not random sets. In other words, each time the select statements above are run, exactly the same sets will result, as long as no new rows are inserted. Rather than use this SQL statement every time the test set is desired, a test set view and training set view can be defined as ... 

There are many other features of plpgsql that make it useful. There are variables that can hold entire rows of a table, loops that iterate over rows returned from a select statement, methods of handling errors, and ways of executing dynamically generated SQL strings. These are described in the on-line documentation1 and books on PostgreSQL.2... 

This insert statement is a bit more complex than the one that inserted rows into the vla4.structure table. In that table, only one row was returned from the mol file mol function. The mol file properties function returns multiple rows for each molfile, when there are multiple properties for each molfile. The second select statement above (the one in parentheses and identified with the name atmp) selects all the rows for each molfile. The first select statement selects all the columns from each returned row from molfile properties. These are then inserted into the vla4. property table. 

The bind columns function requires as many perl variables as there are columns in the select statement. The names used here are indicative of the columns selected, making the code more understandable. The use of bind columns is also very efficient. 

R is a program used to compute statistical results for sets of data. One of the commonly used data types in R is the data frame. This has many similarities to tables of data in a relational database, or tables resulting from an SQL select statement. Using the RODBC module, R can communicate with a RDMBS using SQL to read data into a data frame form and to write a data frame to an RDBMS table. 

This function can then be used to easily estimate a logp value for any valid SMILES. For example, the following SQL computes the same result as the select statement above. 

Some selected statements from the draft report of the Subcommittee on Patent and Information Policy are shown in Figure 14 (21). The statements show a complete rejection of the concept of any legislated or standardized approach based on profit-sharing. 

SQL statements exist for defining the structure of the database as well as manipulating its data. You may create and drop tables from the database, although mtmy people use tools provided by the DBMS software itself for these tasks. SQL may also be used to insert, update, and delete data from existing tables. The most common task performed by users, however, is data retrieval. For this, the SELECT statement is used. The typical syntax for SELECT is as follows ... 

The SELECT statement may also be used to join data from different tables based on their common field values. For example, in order to produce a list of employee names and their departments, you would write ... 

It is also possible to sort the results returned by a query by adding the ORDER BY clause to the SELECT statement. For example, to create an alphabetical listing of department names and IDs, you would write ... 

Planning for the future or planning in mechanical engineering can be approached in many ways. For this book, it is described as a generalized four step process. These four steps in Planning are, 1) Establish a Statement of the Theme, 2) Describe the Core Background Elements, 3) Analyze the Current Conditions Shortfalls, and 4) Select Statement(s) of the Problem. These four steps in Planning are described in detail as ... 

Analyze the Current Condition s Shortfalls 4. Select Statement(s) of the Problem... 

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