Select from clause

Notice the use of the Join keyword and the additional table name pubchem.substance in the From clause. This is necessary because data from this table is being selected. The additional columns selected are ext datasource name and substance.ext datasource regid in the Select clause. Any columns of interest in the substance table could be selected. Note that since there is a column named ext datasource id in both tables, it is necessary to specify that the column substance.ext datasource regid is desired. Finally, the clause On nci h23.sid= substance, substance id indicates that these columns are related to each other and must be used in the Join. 

Note two additional Join clauses, each with the appropriate On clause naming the columns that relate the tables being joined. The additional columns compound id, compound type, and openeye can smiles are from the compound table. No columns are actually selected from the substance compound table. That table is simply used to affect the many-to-many relationship between the substance and compound tables. 

Notice that each line in the select clause contains columns from only one table. Likewise, each line in the from clause contains one new table name with each table (after the first one) preceded by the join keyword. Each column uses a table name (a table alias) for brevity. Now that all the tables are properly joined, the columns selected can be arranged in any order desired. Some columns can also be removed from the select clause. The compound id and sample id may not be of interest in the final result, since these arbitrary values are used only to maintain relations among the tables. Finally, any additions to the where clause can be added as desired. 

As a relational query language, SQL always returns results that are themselves relation instances. Thus, the basic constructs in SQL cooperate in specifying aspects of the schema as well as the instantiation of a query result. Roughly, the SELECT clause specifies the names of attributes to appear in the result, the FROM clause specifies... 

COMBISULF A process for removing sulfur compounds from the gases from combined-cycle power plants with integrated coal gasification. Carbonyl sulfide is removed by catalytic hydrolysis hydrogen sulfide is removed by selective absorbtion in aqueous MEDA and the sulfur is recovered from both processes by a modified Claus unit. Developed by Krupp Koppers and first operated in Spain in 1996. See PRENFLO. 

RAR [Recycle Absorbtion Regeneration] A process for extracting traces of sulfur compounds from the effluent gases from the Claus process by use of a selective amine absorbent. Developed by KTI. 

UCAP A process for selectively removing residual sulfur dioxide from the tail gas from the Claus process. It had not been commercialized by 1983. 

The direct-oxidation processes for recovery of sulfur from raw gases are also applicable on acid-gas streams. Usually, a direct oxidation process would be applied when a nonselective acid-gas removal system had been employed and the sulfur concentration in the acid gas is relatively low. At higher H2S concentrations, as achieved through selective acid-gas removal, the conventional Claus process appears to be more economic. 

The sour natural gas sulfur recovery industry covers virtually the entire gamut of chemistry. From the sour gas reservoir to the Claus plant end product problems are encountered in thermodynamics, kinetics, corrosion, catalysis, redox, rheology and the environment - plus all the rest In reviewing recent developments in such a wide ranging field it is only possible to select examples. It is hoped, however, that these highlights will serve to illustrate the dynamism of the industry in recent years and the progress it has made in developing a new source of one of the world s most basic and essential elements in an environmentally acceptable manner. 

This statement translates to "Select everything from the table named RXN, where the SMILES field contains the substructure string for benzoic acid as a product". The = clause is an artifact of the data cartridge implementation it does not necessarily mean that only a single occurrence of the benzoic acid substructure should be found. 

Figure 2.7 Multiple-slit diffraction pattern for electrons, obtained by Claus Jonsson. Selected as the most beautiful experiment in the history of physics" by Physics World in 2002. (From Z. Phys. 161, 468, (1961). Used by permission of Dr. Claus Jonsson, Tubingen.)...

The model is implemented with input to the connectionist model in the lower portion of Figure 15.1. The input consists of a single binary vector representing all information in the multistep problem (as shown in Table 15.1). Because the vector contains all the information from all the situations represented in the problem, pointers to more than one situation typically occur. The connectionist network identifies the most salient situation and passes that information to the elaboration production system. Using the output from the connectionist network together with the clause information, this part of the model determines the best configuration of problem data to represent the selected situation. The production system selects a subset of clauses to represent each configuration. 

In the SQL examples discussed previously, tables were joined with each other using the on condition to correlate the appropriate rows and a final where clause to restrict the selection of data. Without using the on condition, every row of one table would be joined with every row of the other, resulting in more rows than desired. Sometimes, one wishes to join all rows from one table with all rows from another to result in all possible combinations of rows. Unless the tables are relatively small, this may still result in more rows than desired. For example, in a table of nci.structures containing only 250,000 structures, combining all rows with each other would result in 62,500,000,000 rows Even if a where clause is used to restrict the number of selected rows, it is inefficient (and unnecessary) to produce combinations in this way. 

The amine section absorbs most of the hydrogen sulfide from the gas while coabsorbing as little carbon dioxide as possible. These acid gases are recycled to the inlet of the Claus unit and become part of its feed. Because the solvent selects hydrogen sulfide and rejects most of the carbon dioxide, the size of the Claus SRU is increased by only 5-6% because of recycling inert carbon dioxide. 

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