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I am learning how to use ArcGIS and I am unsure how to assign appropriate buffer distance to each lake size classes for a homework assignment, please see the picture below. The goal is to place specific values in the newly created field that assign Buffdist to Size_Cls.

1= 50 
2= 150 
3= 500

I get to opening the Select by Attribute table, but any input I try gives:

An invalid SQL was used.

Does anyone have any suggestions or any place to redirect me to find how to solve my problem?

Select by Attribute problem

  • your SQL selection for selecting the first lake should be (without bracket): ( Lakes_ID = 1 ) – Florjan Nov 27 '18 at 8:42
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Select by Attribute using the following SQL statement

"SIZE_CLS" = 1

Then right click on the buffdist column header and select Field Calculator Here just type 50 in the white box at the bottom. This will actually perform the operation

buffdist = 50

Repeat for the other SIZE_CLS

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The "select by attribute" tools are pretty fussy about brackets and quotes and so forth, so even though you can type in the pane at the bottom, it's going to lead to syntax problems unless you know the syntax pretty well. Stick to the dialog buttons as much as you can. As stated in Alessio's answer, you want something like "SIZE_CLS" = 1 as your query expression.

Think of the query expression as a true-false expression that will get tested one at a time against each feature, and the features where it is true get put into the selection.

You can also look up SQL syntax online if you note that in the ArcGIS query builder, it always inserts a fixed starting part of the query of "SELECT * FROM x where".

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