7 Control Logic 🔄
In SQL queries, you can incorporate control logic such as:
While loops 🔄
If.. elseif.. else... endif blocks ⚖️
For while loops, the structure is:
markdownWHILE expression;
<statements>
WEND
For IF statements:
phpIF expression
<statements>
ELSEIF expression
<statements>
ELSE
<statements>
ENDIF
You can even use the BREAK
keyword to exit loops. For instance:
bashIF $x>0 AND $y>0
BREAK
ENDIF
This will break out of the loop containing the BREAK
keyword.
When using a WHILE
loop in SQL, a progress bar appears, allowing you to interrupt the query if needed.
8 Variables 📦 To temporarily store values for use in subsequent clauses without saving them post-query, variables come handy. They offer:
- Faster execution as they aren't written to the database 🚀.
- Preservation of user fields for other uses 🛠.
- Utility in setting up GROUP BY or SELECT queries to display results in grids or export them 📊.
Variables, prefixed with a dollar sign $
, are automatically linked with specific object types, ensuring compatibility.
9 Other Variables 🌐 Beyond 'normal' variables, there are scalar variables and list variables.
9.1 Scalar Variables 🔢
Scalar variables hold a single value and are defined using the LET
statement. For instance:
bashLET $flag = "XP"
LET $threshold = 123.4
You can display all scalar values with the SCALARS
keyword.
9.2 List Variables 📝 List variables work with 'list variable functions'. They're defined as:
bashLIST $widths = 100, 300, 500, 700, 900
Functions like LEN
, RINDEX
, LOOKUP
, LOOKUPFN
, MEMBER
, INDEX
, and AREF
can be used with these lists.
9.3 Table variables 📊 These are utilized in GROUP BY clauses, especially when the results are required in an implicit join.
9.4 Save and Load scalar and list variables 💾 You can save and load variables to and from files. The filename can be a string or a scalar variable holding a string. For instance:
bashSAVE $x,$y,$xl,$yl,$zl TO FILE 'd:\temp\filename.dat'
Remember to define all variables in advance, such as:
phpLET $x = null;
LIST $x;
This is the current method to alter list variables.
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