The first parameter is the literal or column value on which you want the SUBSTR function to operate. The second parameter is the position of the starting character for the substring, and the optional third parameter is the number of characters to be included in the substring.If the third parameter is not specified, the SUBSTR function will return the remainder of the string.he second parameter is the position of the starting character for the substring, and the optional third parameter is the number of characters to be included in the substring. If the third parameter is not specified, the SUBSTR function will return the remainder of the string.
There are two basic types of metamorphic rocks. Foliated metamorphic rocks such as gneiss, phyllite, schist, and slate have a layered or banded appearance that is produced by exposure to heat and directed pressure. Non-foliated metamorphic rocks such as hornfels, marble, quartzite, and novaculite do not have a layered or banded appearance.
Gneissic rocks are usually medium-to coarse-foliated; they are largely recrystallized but do not carry large quantities of micas, chlorite or other platy minerals. Gneisses that are metamorphosed igneous rocks or their equivalent are termed granite gneisses, diorite gneisses, etc.neissic rocks are usually medium-to coarse-foliated; they are largely recrystallized but do not carry large quantities of micas, chlorite or other platy minerals. Gneisses that are metamorphosed igneous rocks or their equivalent are termed granite gneisses, diorite gneisses, etc.