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\author{datamansam}
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  /Title (database-and-sql-query-optimisation.pdf)
  /Creator (Cheatography)
  /Author (datamansam)
  /Subject (DataBase and SQL Query Optimisation Cheat Sheet)
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        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
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    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{DataBase and SQL Query Optimisation Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{datamansam} via \textcolor{DarkBackground}{\uline{cheatography.com/139410/cs/29908/}}}
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  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}datamansam \\
  \uline{cheatography.com/datamansam} \\
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 2nd June, 2022.\\
   Page {\thepage} of \pageref{LastPage}.
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  Measure your website readability!\\
  www.readability-score.com
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\begin{document}
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\begin{multicols*}{2}

\begin{tabularx}{8.4cm}{x{2.8 cm} x{5.2 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Quick Solutions to SQL Performance Problems}}  \tn
% Row 0
\SetRowColor{LightBackground}
Acceptable Performance & How Quickly Should Our Scripts Run? Somethimes expectations are unrelistic \tn 
% Row Count 3 (+ 3)
% Row 1
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Utility & Some queries or other database uses are not necessary \tn 
% Row Count 6 (+ 3)
% Row 2
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Time Shifting & Run demanding queries off peek \tn 
% Row Count 8 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{4 cm} x{4 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{DataBase Optimisation}}  \tn
% Row 0
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\mymulticolumn{2}{x{8.4cm}}{Architects aims are to:} \tn 
% Row Count 1 (+ 1)
% Row 1
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Reducing or eliminating data redundancy. & Preventing data inconsistencies and inaccuracies. \tn 
% Row Count 4 (+ 3)
% Row 2
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Ensuring the correctness and integrity of your data. & Facilitating rapid data lookup, retrieval, and analysis. \tn 
% Row Count 7 (+ 3)
% Row 3
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\mymulticolumn{2}{x{8.4cm}}{In-Memory Databases} \tn 
% Row Count 8 (+ 1)
% Row 4
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\mymulticolumn{2}{x{8.4cm}}{Improve speed on data retrieval} \tn 
% Row Count 9 (+ 1)
% Row 5
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In-memory databases keep all data set in computer's memory - RAM & Traditional databases store data on hard drive (HDD or SSD) \tn 
% Row Count 13 (+ 4)
% Row 6
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\mymulticolumn{2}{x{8.4cm}}{So in-memory DBs do not need to perform disk read/write operations to return data} \tn 
% Row Count 15 (+ 2)
% Row 7
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\mymulticolumn{2}{x{8.4cm}}{Saving memory through normalisation} \tn 
% Row Count 16 (+ 1)
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1nf & Each cell in the table can have only one value, \tn 
% Row Count 19 (+ 3)
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2nf & Each of the attributes should be fully dependent on the entire primary ke \tn 
% Row Count 23 (+ 4)
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 & For instance, an attribute "age" that depends on "birthdate" which in turn depends on "studentID"  wouldn't meet 2nf \tn 
% Row Count 30 (+ 7)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
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\begin{tabularx}{8.4cm}{x{4 cm} x{4 cm} }
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\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{DataBase Optimisation (cont)}}  \tn
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 & Furthermore, a table with a primary key made up of multiple fields violates the second normal form if one or more of the other fields do not depend on every part of the key. \tn 
% Row Count 9 (+ 9)
% Row 12
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3nf & Every non-key column be independent of every other column. If changing a value in one non-key column causes another value to change, that table does not meet the third normal form. \tn 
% Row Count 18 (+ 9)
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\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Establish a connection to query a database}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{from sqlalchemy import create\_engine \newline import pandas as pd \newline  \newline engine = \seqsplit{create\_engine('sqlite:///Northwind}.sqlite')} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{4 cm} x{4 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{SQL Diagraming}}  \tn
% Row 0
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\mymulticolumn{2}{x{8.4cm}}{1.	Monitor Wait Time 2.	Review the Execution Plan 3.	Gather Object Information 4.	Find the Driving Table 5.	Identify Performance Inhibitors} \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
1, Wait Times & SQL Server incorporates wait types that allow you to monitor not only the total wait time but also each step of the query as it's processed through the database. W \tn 
% Row Count 12 (+ 9)
% Row 2
\SetRowColor{LightBackground}
2. Review rows ratio between detail and lookup tables & calculate the relative number of records required for the join criteria (that is, the average ratio of rows related between the detail table and lookup tables). \tn 
% Row Count 20 (+ 8)
% Row 3
\SetRowColor{white}
3. Gather Object Info & Determine which tables contain the detailed information and which tables are the master or lookup tables \tn 
% Row Count 26 (+ 6)
% Row 4
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Find the cardinality and distributions of a column & Find out the row count for each table involved. \tn 
% Row Count 29 (+ 3)
% Row 5
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4. Find the Driving Table & By using the driving table, we can query with the table that returns the least data \tn 
% Row Count 34 (+ 5)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
\columnbreak
\begin{tabularx}{8.4cm}{x{4 cm} x{4 cm} }
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\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{SQL Diagraming (cont)}}  \tn
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Next, look at the filtering predicates to find which table to drive the query with & The table that filters out most records is our driving table \tn 
% Row Count 5 (+ 5)
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\end{tabularx}
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\begin{tabularx}{8.4cm}{x{4.96 cm} x{3.04 cm} }
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\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Altering SQL Queries}}  \tn
% Row 0
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\mymulticolumn{2}{x{8.4cm}}{Ensure the Schema in columns we join on match} \tn 
% Row Count 1 (+ 1)
% Row 1
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\mymulticolumn{2}{x{8.4cm}}{Ensure Data Types are the same} \tn 
% Row Count 2 (+ 1)
% Row 2
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Ensure Character Encoding are the same & Both using the same UTF \tn 
% Row Count 4 (+ 2)
% Row 3
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\mymulticolumn{2}{x{8.4cm}}{Avoid Using GroupBy and Distinct together} \tn 
% Row Count 5 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{3.92 cm} x{4.08 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Checkpoints During Query Optimisation}}  \tn
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Checkpoints to evaluate as we optimise & Query Performs Adequately \tn 
% Row Count 2 (+ 2)
% Row 1
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 & Resources required are expensive \tn 
% Row Count 4 (+ 2)
% Row 2
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 & Reached a point of diminishing returns for optimisation \tn 
% Row Count 7 (+ 3)
% Row 3
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 & A completely different solution is discovered \tn 
% Row Count 10 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
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\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{\# To use SQL}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{\# Creating the context manager  \newline con = engine.connect() \newline  \newline rs = con.execute("SELECT * FROM Orders")} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{\# To use Pandas on entire table}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{df = \seqsplit{pd.DataFrame(rs.fetchall())} \newline df.columns = rs.keys() \newline  \newline con.close()} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{\# Using Pandas on part of a table}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{df = \seqsplit{pd.read\_sql\_query("SELECT} OrderID, CompanyName FROM Orders \newline INNER JOIN Customers on Orders.CustomerID = Customers.CustomerID", engine) \newline print(df.head())} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}