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03_ABAP_SQL.md
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03_ABAP_SQL.md
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# ABAP SQL: Working with Persisted Data in Database Tables
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# ABAP SQL in Use
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- [ABAP SQL: Working with Persisted Data in Database Tables](#abap-sql-working-with-persisted-data-in-database-tables)
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- [Database Tables in AS ABAP in a Nutshell](#database-tables-in-as-abap-in-a-nutshell)
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- [ABAP SQL in Use](#abap-sql-in-use)
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- [ABAP SQL Intro](#abap-sql-intro)
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- [Reading Data Using SELECT](#reading-data-using-select)
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- [Basic Syntax](#basic-syntax)
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- [Executable Example](#executable-example)
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## Database Tables in AS ABAP in a Nutshell
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## ABAP SQL Intro
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Database tables in [AS
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ABAP](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenas_abap_glosry.htm "Glossary Entry")
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...
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- [ABAP SQL](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abensql_glosry.htm) is a subset of [SQL](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abensql_glosry.htm "Glossary Entry")
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which is the standardized language for accessing databases.
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- The main ABAP SQL keywords to read and change data are the
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following:
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| Keyword | Purpose |
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| -------- | ------------------------------------------------------------------------- |
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| `SELECT` | Reads data from database tables |
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| `INSERT` | Adds rows to database tables |
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| `UPDATE` | Changes the content of rows of database tables |
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| `MODIFY` | Inserts rows into database tables or changes the content of existing rows |
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| `DELETE` | Deletes rows from database tables |
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- ABAP SQL statements use the ABAP SQL interface. This interface transforms all ABAP SQL statements that access the standard database of an AS ABAP to platform-dependent SQL and forwards the results to the database system.
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- Find more information in the (sub)topics in the ABAP Keyword Documentation [here](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabap_sql.htm).
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- Generally bear in mind the [performance notes ](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabap_sql_perfo.htm) when using
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ABAP SQL. The considerations there are not relevant for this cheat sheet since
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the focus is on syntactical options.
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- are objects of the [ABAP Dictionary
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(DDIC)](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabap_dictionary_glosry.htm "Glossary Entry")
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- consist of table rows and columns; each row represents a data record
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whose components (or fields) are available in columns; each
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component has a data type.
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- are [relational
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database](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenrelational_database_glosry.htm "Glossary Entry")
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tables, i. e. information can be stored in multiple database tables
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that are related to each other.
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- For example, there might be a table containing information on
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flight connections, flight destinations and times, another table
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is related to this one and includes further details on the
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flights like occupied seats in the plane or price details.
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- Such tables define a relationship using [foreign
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key](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenddic_database_tables_forkeyrel.htm)
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relations.
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- have at least one key, i.e. the [primary
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key](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenprimary_key_glosry.htm "Glossary Entry"),
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to uniquely identify table rows; this might be one or more columns
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at the beginning of each database table.
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- are either
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cross-[client](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenclient_glosry.htm "Glossary Entry")
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or client-specific to keep the data separated; client-specific
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tables, which are the vast majority of database tables, include a
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client field (often named `MANDT`) as their first key
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field.
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- Note: ABAP SQL ensures that a statement only
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manipulates data from the current client.
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- have a [flat
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structure](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenflat_structure_glosry.htm "Glossary Entry")
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type.
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- are physically created on the database when activated - in contrast
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to [internal
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tables](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abeninternal_table_glosry.htm "Glossary Entry").
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Plus, a globally available [structured
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type](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenstructured_type_glosry.htm "Glossary Entry")
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of the same name is created, too. Hence, in an ABAP program, a
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database table's name can be used to declare data objects, for
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example, internal tables. These can be accessed by ABAP SQL, too.
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- are primarily processed through ABAP SQL statements that use
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[structures](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenstructure_glosry.htm "Glossary Entry")
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for single rows and internal tables for multiple rows to be
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processed.
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<details>
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<summary>Excursion: Views</summary>
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<summary>Excursion: Database Tables and Views</summary>
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<br>
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This section provides bullet points on database tables and views which contain persisted data. Note that the code snippets in this cheat sheet focus on database tables as [data source](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abendata_source_glosry.htm "Glossary Entry") for ABAP SQL statements.
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**Database tables in [AS ABAP](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenas_abap_glosry.htm "Glossary Entry") ...**
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- are objects of the [ABAP Dictionary (DDIC)](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabap_dictionary_glosry.htm "Glossary Entry"). The term *database table* describes a physical database table in the current [standard database](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenstandard_db_glosry.htm).
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- are two-dimensional matrices consisting of rows and columns.
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- contain a [table key](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abentable_key_glosry.htm), i. e. a field or a combination of fields uniquely identifies every row in a table. A [primary key](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenprimary_key_glosry.htm) must exist for every database table.
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- Note the concept of [foreign keys](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenforeign_key_glosry.htm) in which one or more columns of a database table can be primary keys of another table. See more information [here](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenddic_database_tables_forkey.htm).
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- have a [flat structure](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenflat_structure_glosry.htm "Glossary Entry")
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type. Plus, the definition of database tables consists of [technical](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenddic_database_tables_techstruc.htm) and [semantic](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenddic_database_tables_semastruc.htm) properties.
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- can be referenced as a data type and can be accessed using ABAP SQL.
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Find more information in the respective (sub)topics in the ABAP Keyword Documentation [here](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenddic_database_tables.htm).
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**Views ...**
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- are further ABAP Dictionary objects for grouping particular data.
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- combine columns of one or more database tables.
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- are further ABAP Dictionary objects for grouping columns from one or more database tables, among others.
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- usually realize a
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[join](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenjoin_glosry.htm "Glossary Entry")
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with defined [join
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conditions](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenjoin_condition_glosry.htm "Glossary Entry").
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- Note:
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- Similar to database tables, the columns of such a view form a
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flat structure. Hence, the view's name can be used, for example, to declare
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data objects, too.
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flat structure. Hence, the view's name can be used, for example, as [data types](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abendata_type_glosry.htm) to declare
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[data objects](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abendata_object_glosry.htm), too.
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- The views can be accessed by ABAP SQL, especially for reading
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purposes using `SELECT`.
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@@ -137,49 +123,10 @@ Views](https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm
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editor)
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- are, in contrast to External Views, supported by all database
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systems (that support the ABAP CDS characteristics).
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> **💡 Note**<br>
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> The code snippets below focus on database tables as [data
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source](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abendata_source_glosry.htm "Glossary Entry")
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for ABAP SQL statements.
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</details>
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<p align="right">(<a href="#top">back to top</a>)</p>
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## ABAP SQL Intro
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- ABAP-specific form of standard [Structured Query Language
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(SQL)](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abensql_glosry.htm "Glossary Entry")
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which is the common language to access database tables.
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- What happens behind the scenes when using an ABAP SQL statement?
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- Generally speaking, tables in relational database systems have a
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programming interface allowing table access using standard SQL,
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however, these interfaces are not entirely uniform and can have
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individual characteristics.
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- To make AS ABAP independent of the database used, the ABAP SQL
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statements are converted to the corresponding [Native
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SQL](https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abennative_sql_glosry.htm "Glossary Entry")
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statements of the current database system. In doing so, ABAP SQL
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allows a hassle-free and uniform access to the database tables
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no matter what database system is used.
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- The main ABAP SQL keywords to read and change data are the
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following:
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| Keyword | Purpose |
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| -------- | ------------------------------------------------------------------------- |
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| `SELECT` | Reads data from database tables |
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| `INSERT` | Adds rows to database tables |
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| `UPDATE` | Changes the content of rows of database tables |
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| `MODIFY` | Inserts rows into database tables or changes the content of existing rows |
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| `DELETE` | Deletes rows from database tables |
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- For a good level of performance of your ABAP programs when using
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ABAP SQL, you should follow the rules in the performance notes
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outlined
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[here](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabap_sql_perfo.htm).
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The considerations there are not relevant for this cheat sheet since
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the focus is on syntactical options.
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## Reading Data Using SELECT
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### Basic Syntax
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